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SNMPD.CONF(5)                      Net-SNMP                      SNMPD.CONF(5)



NAME
       snmpd.conf - configuration file for the Net-SNMP SNMP agent

DESCRIPTION
       The  Net-SNMP agent uses one or more configuration files to control its
       operation  and  the  management  information  provided.   These   files
       (snmpd.conf  and  snmpd.local.conf)  can  be  located in one of several
       locations, as described in the snmp_config(5) manual page.

       The (perl) application snmpconf can be used to  generate  configuration
       files for the most common agent requirements.  See the snmpconf(1) man-
       ual page for more information, or try running the command:

              snmpconf -g basic_setup

       There are a large number of directives that can be specified, but these
       mostly fall into four distinct categories:

       o      those controlling who can access the agent

       o      those configuring the information that is supplied by the agent

       o      those controlling active monitoring of the local system

       o      those concerned with extending the functionality of the agent.

       Some directives don't fall naturally into any of these four categories,
       but this covers the majority of the contents of  a  typical  snmpd.conf
       file.   A full list of recognised directives can be obtained by running
       the command:

              snmpd -H

AGENT BEHAVIOUR
       Although most configuration  directives  are  concerned  with  the  MIB
       information  supplied  by  the agent, there are a handful of directives
       that control the behaviour of snmpd considered simply as a daemon  pro-
       viding a network service.

       agentaddress [<transport-specifier>:]<transport-address>[,...]
              defines  a  list  of  listening  addresses,  on which to receive
              incoming SNMP requests.  See the section LISTENING ADDRESSES  in
              the  snmpd(8)  manual page for more information about the format
              of listening addresses.

              The default behaviour is to listen on UDP port 161 on  all  IPv4
              interfaces.

       agentgroup {GROUP|#GID}
              changes  to  the  specified  group  after  opening the listening
              port(s).  This may refer to  a  group  by  name  (GROUP),  or  a
              numeric group ID starting with '#' (#GID).

       agentuser {USER|#UID}
              changes  to  the  specified  user  after  opening  the listening
              port(s).  This may refer to a user by name (USER), or a  numeric
              user ID starting with '#' (#UID).

       leave_pidfile yes
              instructs  the  agent  to  not  remove its pid file on shutdown.
              Equivalent to specifying "-U" on the command line.

       maxGetbulkRepeats NUM
              Sets the maximum number of responses allowed for a single  vari-
              able  in  a getbulk request.  Set to 0 to enable the default and
              set it to -1 to enable unlimited.  Because memory  is  allocated
              ahead  of time, sitting this to unlimited is not considered safe
              if your user population can not be  trusted.   A  repeat  number
              greater than this will be truncated to this value.

              This is set by default to -1.

       maxGetbulkResponses NUM
              Sets  the  maximum  number  of  responses  allowed for a getbulk
              request.  This is set by default to 100.  Set to 0 to enable the
              default and set it to -1 to enable unlimited.  Because memory is
              allocated ahead of time, sitting this to unlimited is  not  con-
              sidered safe if your user population can not be trusted.

              In general, the total number of responses will not be allowed to
              exceed the  maxGetbulkResponses  number  and  the  total  number
              returned  will be an integer multiple of the number of variables
              requested times the calculated number of repeats  allow  to  fit
              below this number.

              Also not that processing of maxGetbulkRepeats is handled first.

   SNMPv3 Configuration
       SNMPv3  requires  an SNMP agent to define a unique "engine ID" in order
       to respond to SNMPv3 requests.  This ID  will  normally  be  determined
       automatically,   using   two  reasonably  non-predictable  values  -  a
       (pseudo-)random number and the current uptime in seconds. This  is  the
       recommended  approach.  However  the  capacity  exists  to  define  the
       engineID in other ways:

       engineID STRING
              specifies that the engineID should be built from the given  text
              STRING.

       engineIDType 1|2|3
              specifies  that  the  engineID  should  be  built  from the IPv4
              address (1), IPv6 address (2) or MAC  address  (3).   Note  that
              changing  the  IP  address  (or  switching the network interface
              card) may cause problems.

       engineIDNic INTERFACE
              defines which interface to use when determining the MAC address.
              If  engineIDType  3 is not specified, then this directive has no
              effect.

              The default is to use eth0.

ACCESS CONTROL
       snmpd supports the View-Based Access Control Model (VACM) as defined in
       RFC  2575,  to control who can retrieve or update information.  To this
       end, it recognizes  various  directives  relating  to  access  control.
       These fall into four basic groups.

   SNMPv3 Users
       createUser  [-e  ENGINEID]  username (MD5|SHA) authpassphrase [DES|AES]
       [privpassphrase]

              MD5 and SHA are the authentication types to use.   DES  and  AES
              are  the privacy protocols to use.  If the privacy passphrase is
              not specified, it is assumed to be the same as  the  authentica-
              tion  passphrase.   Note  that the users created will be useless
              unless they are also added to the  VACM  access  control  tables
              described above.

              SHA  authentication  and  DES/AES  privacy require OpenSSL to be
              installed and the agent to be built with OpenSSL  support.   MD5
              authentication may be used without OpenSSL.

              Warning: the minimum pass phrase length is 8 characters.

              SNMPv3 users can be created at runtime using the snmpusm(1) com-
              mand.

              Instead of figuring out how to use this directive and  where  to
              put   it   (see  below),  just  run  "net-snmp-config  --create-
              snmpv3-user" instead, which will add one of these lines  to  the
              right place.

              This     directive     should     be     placed     into     the
              /var/lib/snmp/snmpd.conf file instead of the other normal  loca-
              tions.  The reason is that the information is read from the file
              and then the line is removed (eliminating  the  storage  of  the
              master password for that user) and replaced with the key that is
              derived from it.  This key is a localized key, so that if it  is
              stolen  it can not be used to access other agents.  If the pass-
              word is stolen, however, it can be.

              If you need to localize the user to a particular EngineID  (this
              is  useful  mostly  in the similar snmptrapd.conf file), you can
              use the -e argument to specify an EngineID as a hex  value  (EG,
              "0x01020304").

              If  you  want  to  generate either your master or localized keys
              directly, replace the given password with a hexstring (preceeded
              by  a  "0x")  and  precede  the  hex  string by a -m or -l token
              (respectively).  EGs:

              [these keys are *not* secure but are easy to visually parse for
              counting purposes.  Please generate random keys instead of using
              these examples]

              createUser myuser SHA -l 0x0001020304050607080900010203040506070809 AES -l 0x00010203040506070809000102030405
              createUser myuser SHA -m 0x0001020304050607080900010203040506070809 AES -m 0x0001020304050607080900010203040506070809

              Due to the way localization happens, localized privacy keys  are
              expected  to be the length needed by the algorithm (128 bits for
              all supported algorithms).  Master encryption keys, though, need
              to  be  the  length required by the authentication algorithm not
              the length required by the encrypting algorithm (MD5: 16  bytes,
              SHA: 20 bytes).

   Traditional Access Control
       Most  simple  access  control  requirements  can be specified using the
       directives rouser/rwuser (for SNMPv3) or  rocommunity/rwcommunity  (for
       SNMPv1 or SNMPv2c).

       rouser USER [noauth|auth|priv [OID | -V VIEW [CONTEXT]]]

       rwuser USER [noauth|auth|priv [OID | -V VIEW [CONTEXT]]]
              specify  an  SNMPv3 user that will be allowed read-only (GET and
              GETNEXT) or read-write (GET, GETNEXT  and  SET)  access  respec-
              tively.   By  default,  this will provide access to the full OID
              tree for authenticated (including  encrypted)  SNMPv3  requests,
              using  the  default  context.   An  alternative minimum security
              level can be specified using noauth  (to  allow  unauthenticated
              requests),  or  priv  (to  enforce  use of encryption).  The OID
              field restricts access for that user to the  subtree  rooted  at
              the  given OID, or the named view.  An optional context can also
              be specified, or "context*" to denote a context prefix.   If  no
              context  field  is  specified  (or  the  token "*" is used), the
              directive will match all possible contexts.

       rocommunity COMMUNITY [SOURCE [OID | -V VIEW [CONTEXT]]]

       rwcommunity COMMUNITY [SOURCE [OID | -V VIEW [CONTEXT]]]
              specify an SNMPv1 or SNMPv2c  community  that  will  be  allowed
              read-only (GET and GETNEXT) or read-write (GET, GETNEXT and SET)
              access respectively.  By default, this will  provide  access  to
              the  full  OID  tree for such requests, regardless of where they
              were sent from. The SOURCE token can be used to restrict  access
              to  requests  from the specified system(s) - see com2sec for the
              full details.  The OID field restricts access for that community
              to the subtree rooted at the given OID, or named view.  Contexts
              are typically less relevant to  community-based  SNMP  versions,
              but the same behaviour applies here.

       rocommunity6 COMMUNITY [SOURCE [OID | -V VIEW [CONTEXT]]]

       rwcommunity6 COMMUNITY [SOURCE [OID | -V VIEW [CONTEXT]]]
              are  directives relating to requests received using IPv6 (if the
              agent supports such transport domains).  The  interpretation  of
              the SOURCE, OID, VIEW and CONTEXT tokens are exactly the same as
              for the IPv4 versions.

       In each case, only one directive should be specified for a given SNMPv3
       user,  or  community  string.   It  is  not appropriate to specify both
       rouser and rwuser directives referring to  the  same  SNMPv3  user  (or
       equivalent  community  settings). The rwuser directive provides all the
       access of rouser (as well as allowing SET  support).   The  same  holds
       true for the community-based directives.

       More  complex  access  requirements (such as access to two or more dis-
       tinct OID subtrees, or different views for GET and SET requests) should
       use  one  of the other access control mechanisms.  Note that if several
       distinct communities or SNMPv3 users need to be granted the same  level
       of access, it would also be more efficient to use the main VACM config-
       uration directives.

   VACM Configuration
       The full flexibility of the VACM is available using four  configuration
       directives  -  com2sec,  group,  view and access.  These provide direct
       configuration of the underlying VACM tables.

       com2sec  [-Cn CONTEXT] SECNAME SOURCE COMMUNITY

       com2sec6 [-Cn CONTEXT] SECNAME SOURCE COMMUNITY
              map an SNMPv1 or SNMPv2c community string to a security  name  -
              either  from a particular range of source addresses, or globally
              ("default").  A restricted source can either be a specific host-
              name  (or  address),  or a subnet - represented as IP/MASK (e.g.
              10.10.10.0/255.255.255.0), or IP/BITS (e.g.  10.10.10.0/24),  or
              the IPv6 equivalents.

              The  same  community string can be specified in several separate
              directives (presumably with different source  tokens),  and  the
              first  source/community  combination  that  matches the incoming
              request will be selected.  Various source/community combinations
              can also map to the same security name.

              If a CONTEXT is specified (using -Cn), the community string will
              be mapped to a security name in the named SNMPv3 context. Other-
              wise the default context ("") will be used.

       com2secunix [-Cn CONTEXT] SECNAME SOCKPATH COMMUNITY
              is the Unix domain sockets version of com2sec.

       group GROUP {v1|v2c|usm} SECNAME
              maps  a  security  name (in the specified security model) into a
              named group.  Several group  directives  can  specify  the  same
              group name, allowing a single access setting to apply to several
              users and/or community strings.

              Note that groups must be set up for the two community-based mod-
              els separately - a single com2sec (or equivalent) directive will
              typically be accompanied by two group directives.

       view VNAME TYPE OID [MASK]
              defines a named "view" - a subset of the overall OID tree.  This
              is  most  commonly a single subtree, but several view directives
              can be given with the same view name (VNAME), to build up a more
              complex   collection  of  OIDs.   TYPE  is  either  included  or
              excluded, which can again define a more  complex  view  (e.g  by
              excluding certain sensitive objects from an otherwise accessible
              subtree).

              MASK is a list of hex octets (optionally  separated  by  '.'  or
              ':')  with  the  set bits indicating which subidentifiers in the
              view OID to match against.  If not specified, this  defaults  to
              matching  the OID exactly (all bits set), thus defining a simple
              OID subtree.  So:
                     view iso1 included .iso  0xf0
                     view iso2 included .iso
                     view iso3 included .iso.org.dod.mgmt  0xf0

              would all define the  same  view,  covering  the  whole  of  the
              'iso(1)' subtree (with the third example ignoring the subidenti-
              fiers not covered by the mask).

              More usefully, the mask can be used to define a view covering  a
              particular  row  (or  rows)  in a table, by matching against the
              appropriate table index value, but skipping the column  subiden-
              tifier:

                     view ifRow4 included .1.3.6.1.2.1.2.2.1.0.4  0xff:a0

              Note that a mask longer than 8 bits must use ':' to separate the
              individual octets.

       access GROUP CONTEXT {any|v1|v2c|usm} LEVEL PREFX READ WRITE NOTIFY
              maps from a group of users/communities (with a particular  secu-
              rity  model  and  minimum security level, and in a specific con-
              text) to one of three views, depending on the request being pro-
              cessed.

              LEVEL is one of noauth, auth, or priv.  PREFX specifies how CON-
              TEXT should be matched  against  the  context  of  the  incoming
              request,  either exact or prefix.  READ, WRITE and NOTIFY speci-
              fies the view to be used for GET*, SET and TRAP/INFORM  requests
              (althought  the  NOTIFY  view is not currently used).  For v1 or
              v2c access, LEVEL will need to be noauth.

   Typed-View Configuration
       The final group of directives extend the  VACM  approach  into  a  more
       flexible  mechanism,  which  can  be  applied  to  other access control
       requirements. Rather than the fixed three views of  the  standard  VACM
       mechanism,  this can be used to configure various different view types.
       As far as the main SNMP agent is concerned, the two main view types are
       read  and  write, corresponding to the READ and WRITE views of the main
       access directive.  See the 'snmptrapd.conf(5)' man page for  discussion
       of other view types.

       authcommunity TYPES  COMMUNITY   [SOURCE [OID | -V VIEW [CONTEXT]]]
              is  an  alternative  to  the rocommunity/rwcommunity directives.
              TYPES will usually be read or read,write respectively.  The view
              specification  can  either  be  an OID subtree (as before), or a
              named view (defined using the view directive) for greater flexi-
              bility.   If this is omitted, then access will be allowed to the
              full OID tree.  If CONTEXT is specified,  access  is  configured
              within  this SNMPv3 context.  Otherwise the default context ("")
              is used.

       authuser   TYPES [-s MODEL] USER  [LEVEL [OID | -V VIEW [CONTEXT]]]
              is an alternative to the rouser/rwuser directives.   The  fields
              TYPES,  OID, VIEW and CONTEXT have the same meaning as for auth-
              community.

       authgroup  TYPES [-s MODEL] GROUP [LEVEL [OID | -V VIEW [CONTEXT]]]
              is a companion to the authuser directive, specifying access  for
              a particular group (defined using the group directive as usual).
              Both authuser and authgroup default to authenticated requests  -
              LEVEL can also be specified as noauth or priv to allow unauthen-
              ticated requests,  or  require  encryption  respectively.   Both
              authuser  and  authgroup  directives also default to configuring
              access for SNMPv3/USM requests - use the '-s' flag to specify an
              alternative  security model (using the same values as for access
              above).

       authaccess TYPES [-s MODEL] GROUP VIEW [LEVEL [CONTEXT]]
              also configures the access for a  particular  group,  specifying
              the  name  and type of view to apply. The MODEL and LEVEL fields
              are interpreted in the same way as for authgroup.  If CONTEXT is
              specified,  access  is configured within this SNMPv3 context (or
              contexts with this prefix if the CONTEXT field ends  with  '*').
              Otherwise the default context ("") is used.

       setaccess GROUP CONTEXT MODEL LEVEL PREFIX VIEW TYPES
              is  a  direct equivalent to the original access directive, typi-
              cally listing the view types as read or read,write as  appropri-
              ate.  (or see 'snmptrapd.conf(5)' for other possibilities).  All
              other fields have the same interpretation as with access.

SYSTEM INFORMATION
       Most of the information reported by the  Net-SNMP  agent  is  retrieved
       from  the  underlying  system,  or  dynamically configured via SNMP SET
       requests (and retained from one run of the agent to  the  next).   How-
       ever,  certain  MIB  objects  can  be  configured or controlled via the
       snmpd.conf(5) file.

   System Group
       Most of the scalar objects in the 'system' group can be  configured  in
       this way:

       sysLocation STRING

       sysContact STRING

       sysName STRING
              set the system location, system contact or system name (sysLoca-
              tion.0, sysContact.0 and sysName.0) for the agent  respectively.
              Ordinarily  these  objects are writeable via suitably authorized
              SNMP SET requests.  However, specifying one of these  directives
              makes the corresponding object read-only, and attempts to SET it
              will result in a notWritable error response.

       sysServices NUMBER
              sets the value of the sysServices.0 object.  For a host  system,
              a  good  value is 72 (application + end-to-end layers).  If this
              directive is not specified, then no value will be  reported  for
              the sysServices.0 object.

       sysDescr STRING

       sysObjectID OID
              sets  the  system  description  or  object  ID  for  the  agent.
              Although these MIB objects are not SNMP-writable,  these  direc-
              tives  can be used by a network administrator to configure suit-
              able values for them.

   Interfaces Group
       interface NAME TYPE SPEED
              can be used to provide appropriate type and speed  settings  for
              interfaces  where  the agent fails to determine this information
              correctly.  TYPE is a type value as given in the IANAifType-MIB,
              and  can  be specified numerically or by name (assuming this MIB
              is loaded).

   Host Resources Group
       This requires that the agent was built with support for the host module
       (which  is  now  included as part of the default build configuration on
       the major supported platforms).

       ignoreDisk STRING
              controls which disk devices are scanned as  part  of  populating
              the  hrDiskStorageTable (and hrDeviceTable).  The HostRes imple-
              mentation code includes a list of disk device patterns appropri-
              ate  for  the  current operating system, some of which may cause
              the agent to block when trying to open  the  corresponding  disk
              devices.   This  might  lead  to  a  timeout  when walking these
              tables, possibly  resulting  in  inconsistent  behaviour.   This
              directive  can  be  used  to  specify particular devices (either
              individually or wildcarded) that should not be checked.

              Note:  Please consult the source (host/hr_disk.c) and check  for
                     the Add_HR_Disk_entry calls relevant for a particular O/S
                     to determine the list of devices that will be scanned.

              The pattern can include one or more wildcard  expressions.   See
              snmpd.examples(5) for illustration of the wildcard syntax.

       skipNFSInHostResources true
              controls whether NFS and NFS-like file systems should be omitted
              from the hrStorageTable (true or 1) or not (false or 0, which is
              the  default).   If  the Net-SNMP agent gets hung on NFS-mounted
              filesystems, you can try setting this to '1'.

       storageUseNFS [1|2]
              controls how NFS and NFS-like file systems should be reported in
              the hrStorageTable.  as 'Network Disks' (1) or 'Fixed Disks' (2)
              Historically, the Net-SNMP agent has reported such file  systems
              as 'Fixed Disks', and this is still the default behaviour.  Set-
              ting this directive to '1' reports such file systems as

   Process Monitoring
       The hrSWRun group of the Host Resources MIB provides information  about
       individual  processes  running on the local system.  The prTable of the
       UCD-SNMP-MIB complements this by reporting on selected services  (which
       may  involve  multiple  processes).   This  requires that the agent was
       built with support for the ucd-snmp/proc module (which is  included  as
       part of the default build configuration).

       proc NAME [MAX [MIN]]
              monitors  the  number  of  processes called NAME (as reported by
              "/bin/ps -e") running on the local system.

              If the number of NAMEd processes is less  than  MIN  or  greater
              than  MAX,  then  the corresponding prErrorFlag instance will be
              set to 1, and a suitable description message  reported  via  the
              prErrMessage instance.

              Note:  This  situation  will not automatically trigger a trap to
                     report the problem - see the  DisMan  Event  MIB  section
                     later.

              If  neither MAX nor MIN are specified (or are both 0), they will
              default to infinity and 1 respectively  ("at  least  one").   If
              only  MAX  is  specified,  MIN  will default to 0 ("no more than
              MAX").

       procfix NAME PROG ARGS
              registers a command that can be run to fix errors with the given
              process  NAME.  This will be invoked when the corresponding prE-
              rrFix instance is set to 1.

              Note:  This command will not be invoked automatically.

              The procfix directive must be specified after the matching  proc
              directive, and cannot be used on its own.

       If  no  proc directives are defined, then walking the prTable will fail
       (noSuchObject).

   Disk Usage Monitoring
       This requires that the agent  was  built  with  support  for  the  ucd-
       snmp/disk  module  (which is included as part of the default build con-
       figuration).

       disk PATH [ MINSPACE | MINPERCENT% ]
              monitors the disk mounted at PATH for available disk space.

              The minimum threshold can either be specified in  Kb  (MINSPACE)
              or  as  a  percentage  of the total disk (MINPERCENT% with a '%'
              character), defaulting to 100Kb if neither  are  specified.   If
              the  free disk space falls below this threshold, then the corre-
              sponding dskErrorFlag instance will be set to 1, and a  suitable
              description message reported via the dskErrorMsg instance.

              Note:  This  situation  will not automatically trigger a trap to
                     report the problem - see the  DisMan  Event  MIB  section
                     later.

       includeAllDisks MINPERCENT%
              configures  monitoring  of  all disks found on the system, using
              the specified (percentage) threshold.  The threshold  for  indi-
              vidual  disks  can  be  adjusted  using suitable disk directives
              (which can come  either  before  or  after  the  includeAllDisks
              directive).

              Note:  Whether   disk   directives   appears   before  or  after
                     includeAllDisks may affect the indexing of the dskTable.

              Only one includeAllDisks directive should  be  specified  -  any
              subsequent copies will be ignored.

              The  list  of  mounted  disks  will be determined when the agent
              starts using the setmntent(3) and getmntent(3), or fopen(3)  and
              getmntent(3),  or setfsent(3)  and  getfsent(3) system calls. If
              none of the above system calls are available then the root  par-
              tition   "/" (which  is  assumed to exist on any UNIX based sys-
              tem) will be monitored.   Disks  mounted  after  the  agent  has
              started will not be monitored.

       If  neither  any  disk  directives or includeAllDisks are defined, then
       walking the dskTable will fail (noSuchObject).

   System Load Monitoring
       This requires that the agent was built with support for either the ucd-
       snmp/loadave module or the ucd-snmp/memory module respectively (both of
       which are included as part of the default build configuration).

       load MAX1 [MAX5 [MAX15]]
              monitors the  load  average  of  the  local  system,  specifying
              thresholds  for  the  1-minute, 5-minute and 15-minute averages.
              If any of these loads exceed the associated maximum value,  then
              the  corresponding  laErrorFlag instance will be set to 1, and a
              suitable  description  message  reported  via  the  laErrMessage
              instance.

              Note:  This  situation  will not automatically trigger a trap to
                     report the problem - see the  DisMan  Event  MIB  section
                     later.

              If  the  MAX15 threshold is omitted, it will default to the MAX5
              value.  If both MAX5 and MAX15 are omitted, they will default to
              the  MAX1  value.  If this directive is not specified, all three
              thresholds will default to a value of DEFMAXLOADAVE.

              If a threshold value of 0 is given, the agent  will  not  report
              errors  via  the relevant laErrorFlag or laErrMessage instances,
              regardless of the current load.

       Unlike the proc and disk directives, walking the  walking  the  laTable
       will  succeed (assuming the ucd-snmp/loadave module was configured into
       the agent), even if the load directive is not present.

       swap MIN
              monitors the amount of swap space available on the local system.
              If  this  falls below the specified threshold (MIN Kb), then the
              memErrorSwap object will be set to 1, and a suitable description
              message reported via memSwapErrorMsg.

              Note:  This  situation  will not automatically trigger a trap to
                     report the problem - see the  DisMan  Event  MIB  section
                     later.
       If this directive is not specified, the default threshold is 16 Mb.

   Log File Monitoring
       This requires that the agent was built with support for either the ucd-
       snmp/file or ucd-snmp/logmatch modules respectively (both of which  are
       included as part of the default build configuration).

       file FILE [MAXSIZE]
              monitors  the size of the specified file (in Kb).  If MAXSIZE is
              specified, and the size of the file exceeds this threshold, then
              the corresponding fileErrorFlag instance will be set to 1, and a
              suitable  description  message  reported  via  the  fileErrorMsg
              instance.

              Note:  This  situation  will not automatically trigger a trap to
                     report the problem - see the  DisMan  Event  MIB  section
                     later.

              A maximum of 20 files can be monitored.

       If no file directives are defined, then walking the fileTable will fail
       (noSuchObject).

       logmatch NAME PATH CYCLETIME REGEX
              monitors the specified file for occurances of the specified pat-
              tern REGEX.

              A maximum of 50 files can be monitored.

       If  no  logmatch directives are defined, then walking the logMatchTable
       will fail (noSuchObject).

ACTIVE MONITORING
       The usual behaviour of an SNMP agent  is  to  wait  for  incoming  SNMP
       requests  and  respond  to them - if no requests are received, an agent
       will typically not initiate any actions. This section describes various
       directives that can configure snmpd to take a more active role.

   Notification Handling
       trapcommunity STRING
              defines  the  default  community  string to be used when sending
              traps.  Note that this directive must be used prior to any  com-
              munity-based trap destination directives that need to use it.

       trapsink HOST [COMMUNITY [PORT]]

       trap2sink HOST [COMMUNITY [PORT]]

       informsink HOST [COMMUNITY [PORT]]
              define  the  address  of  a notification receiver that should be
              sent SNMPv1 TRAPs, SNMPv2c TRAP2s, or  SNMPv2  INFORM  notifica-
              tions  respectively.  See the section LISTENING ADDRESSES in the
              snmpd(8) manual page for more information about  the  format  of
              listening  addresses.   If  COMMUNITY is not specified, the most
              recent trapcommunity string will be used.

              If the transport address does not include an explicit port spec-
              ification,  then  PORT  will be used.  If this is not specified,
              the well known SNMP trap port (162) will be used.

              Note:  This mechanism is being  deprecated,  and  the  listening
                     port  should be specified via the transport specification
                     HOST instead.

              If several sink directives are  specified,  multiple  copies  of
              each  notification  (in  the appropriate formats) will be gener-
              ated.

              Note:  It is not normally appropriate to list two (or all three)
                     sink directives with the same destination.

       trapsess [SNMPCMD_ARGS] HOST
              provides a more generic mechanism for defining notification des-
              tinations.  SNMPCMD_ARGS  should  be  the  command-line  options
              required  for  an equivalent snmptrap (or snmpinform) command to
              send the desired notification.  The option -Ci can be used (with
              -v2c  or  -v3) to generate an INFORM notification rather than an
              unacknowledged TRAP.

              This is the  appropriate  directive  for  defining  SNMPv3  trap
              receivers.  See http://www.net-snmp.org/tutorial/tutorial-5/com-
              mands/snmptrap-v3.html for more information about SNMPv3 notifi-
              cation behaviour.

       authtrapenable {1|2}
              determines  whether  to  generate  authentication  failure traps
              (enabled(1)) or not (disabled(2) - the default).  Ordinarily the
              corresponding  MIB  object  (snmpEnableAuthenTraps.0)  is  read-
              write, but specifying this directive  makes  this  object  read-
              only, and attempts to set the value via SET requests will result
              in a notWritable error response.

   DisMan Event MIB
       The previous directives can be used to configure where traps should  be
       sent, but are not concerned with when to send such traps (or what traps
       should be generated).  This is the domain of the Event MIB -  developed
       by the Distributed Management (DisMan) working group of the IETF.

       This  requires  that  the  agent  was  built  with support for the dis-
       man/event module (which is now included as part of  the  default  build
       configuration for the most recent distribution).

              Note:  The  behaviour  of  the  latest implementation differs in
                     some minor respects from the previous code - nothing  too
                     significant,  but existing scripts may possibly need some
                     minor adjustments.

       iquerySecName NAME

       agentSecName NAME
              specifies the default SNMPv3 username, to be  used  when  making
              internal  queries  to retrieve any necessary information (either
              for evaluating the monitored expression, or building a notifica-
              tion  payload).   These internal queries always use SNMPv3, even
              if normal querying of the agent is done using SNMPv1 or SNMPv2c.

              Note that this user must also be explicitly created (createUser)
              and  given appropriate access rights (e.g. rouser).  This direc-
              tive is purely concerned with defining which user should be used
              - not with actually setting this user up.

       monitor [OPTIONS] NAME EXPRESSION
              defines  a  MIB  object to monitor.  If the EXPRESSION condition
              holds (see below), then  this  will  trigger  the  corresponding
              event,  and either send a notification or apply a SET assignment
              (or both).  Note that the event will  only  be  triggered  once,
              when  the expression first matches.  This monitor entry will not
              fire again until the monitored condition  first  becomes  false,
              and then matches again.  NAME is an administrative name for this
              expression, and is used for indexing  the  mteTriggerTable  (and
              related  tables).   Note also that such monitors use an internal
              SNMPv3 request to retrieve the values being monitored  (even  if
              normal  agent queries typically use SNMPv1 or SNMPv2c).  See the
              iquerySecName token described above.

       EXPRESSION
              There are three types of monitor  expression  supported  by  the
              Event MIB - existence, boolean and threshold tests.

              OID | ! OID | != OID
                     defines  an existence(0) monitor test.  A bare OID speci-
                     fies a present(0) test, which will fire when (an instance
                     of)  the  monitored OID is created.  An expression of the
                     form ! OID specifies an absent(1) test, which  will  fire
                     when the monitored OID is delected.  An expression of the
                     form != OID specifies a changed(2) test, which will  fire
                     whenever  the monitored value(s) change.  Note that there
                     must be whitespace before the OID token.

              OID OP VALUE
                     defines a boolean(1) monitor test.  OP should be  one  of
                     the  defined  comparison operators (!=, ==, <, <=, >, >=)
                     and VALUE should be an integer value to compare  against.
                     Note  that  there must be whitespace around the OP token.
                     A comparison such as OID !=0 will  not  be  handled  cor-
                     rectly.

              OID MIN MAX [DMIN DMAX]
                     defines  a  threshold(2)  monitor  test.  MIN and MAX are
                     integer values, specifying lower  and  upper  thresholds.
                     If  the  value of the monitored OID falls below the lower
                     threshold (MIN) or rises above the upper threshold (MAX),
                     then  the  monitor  entry  will trigger the corresponding
                     event.

                     Note that the rising threshold event  will  only  be  re-
                     armed  when  the  monitored  value  falls below the lower
                     threshold (MIN).  Similarly, the falling threshold  event
                     will be re-armed by the upper threshold (MAX).

                     The optional parameters DMIN and DMAX configure a pair of
                     similar threshold tests, but working with the delta  dif-
                     ferences between successive sample values.

       OPTIONS
              There  are various options to control the behaviour of the moni-
              tored expression.  These include:

              -D     indicates that the expression should be  evaluated  using
                     delta  differences between sample values (rather than the
                     values themselves).

              -d OID

              -di OID
                     specifies a discontinuity  marker  for  validating  delta
                     differences.   A -di object instance will be used exactly
                     as given.  A -d object will have the instance  subidenti-
                     fiers  from  the  corresponding  (wildcarded)  expression
                     object appended.  If the -I flag is specified, then there
                     is no difference between these two options.

                     This option also implies -D.

              -e EVENT
                     specifies the event to be invoked when this monitor entry
                     is triggered.  If this option is not given,  the  monitor
                     entry  will  generate  one  of the standard notifications
                     defined in the DISMAN-EVENT-MIB.

              -I     indicates that the monitored expression should be applied
                     to  the  specified OID as a single instance.  By default,
                     the OID will be treated as a wildcarded object,  and  the
                     monitor expanded to cover all matching instances.

              -i OID

              -o OID define  additional  varbinds to be added to the notifica-
                     tion payload when this  monitor  trigger  fires.   For  a
                     wildcarded expression, the suffix of the matched instance
                     will be added to any OIDs specified using -o, while  OIDs
                     specified  using  -i  will be treated as exact instances.
                     If the -I flag is specified, then there is no  difference
                     between these two options.

                     See strictDisman for details of the ordering of notifica-
                     tion payloads.

              -r FREQUENCY
                     monitors the given expression  every  FREQUENCY  seconds.
                     By  default,  the expression will be evaluated every 600s
                     (10 minutes).

              -S     indicates that the monitor expression should not be eval-
                     uated  when the agent first starts up.  The first evalua-
                     tion will be done once  the  first  repeat  interval  has
                     expired.

              -s     indicates that the monitor expression should be evaluated
                     when the agent first starts up.  This is the default  be-
                     haviour.

                     Note:  Notifications triggered by this initial evaluation
                            will be sent before the coldStart trap.

              -u SECNAME
                     specifies a security name to use for scanning  the  local
                     host,  instead of the default iquerySecName.  Once again,
                     this user must be explicitly created and  given  suitable
                     access rights.

       notificationEvent ENAME NOTIFICATION [-n] [-i OID | -o OID ]*
              defines a notification event named ENAME.  This can be triggered
              from a given monitor entry by specifying  the  option  -e  ENAME
              (see  above).   NOTIFICATION  should be the OID of the NOTIFICA-
              TION-TYPE definition for the notification to be generated.

              If the -n option is given, the notification payload will include
              the  standard varbinds as specified in the OBJECTS clause of the
              notification MIB definition.  This option must  come  after  the
              NOTIFICATION  OID  (and  the relevant MIB file must be available
              and loaded by the agent).  Otherwise,  these  varbinds  must  be
              listed  explicitly  (either here or in the corresponding monitor
              directive).

              The -i OID and -o OID options specify additional varbinds to  be
              appended  to  the notification payload, after the standard list.
              If the monitor entry that triggered this event involved a  wild-
              carded  expression,  the  suffix of the matched instance will be
              added to any OIDs specified using -o, while OIDs specified using
              -i will be treated as exact instances.  If the -I flag was spec-
              ified to the monitor directive,  then  there  is  no  difference
              between these two options.

       setEvent ENAME [-I] OID = VALUE
              defines  a  set event named ENAME, assigning the (integer) VALUE
              to the specified OID.  This can be triggered from a given  moni-
              tor entry by specifying the option -e ENAME (see above).

              If  the monitor entry that triggered this event involved a wild-
              carded expression, the suffix of the matched instance will  nor-
              mally  be  added  to  the  OID.  If the -I flag was specified to
              either of the monitor or setEvent directives, the specified  OID
              will be regarded as an exact single instance.

       strictDisman yes
              The  definition  of  SNMP notifications states that the varbinds
              defined in the OBJECT clause should come  first  (in  the  order
              specified),  followed by any "extra" varbinds that the notifica-
              tion generator feels might be useful.  The most natural approach
              would  be to associate these mandatory varbinds with the notifi-
              cationEvent entry, and append any varbinds associated  with  the
              monitor entry that triggered the notification to the end of this
              list.  This is the default behaviour of the Net-SNMP  Event  MIB
              implementation.

              Unfortunately,  the  DisMan  Event  MIB  specifications actually
              state that the trigger-related varbinds should come first,  fol-
              lowed  by the event-related ones.  This directive can be used to
              restore this strictly-correct (but inappropriate) behaviour.

              Note:  Strict DisMan ordering may result in  generating  invalid
                     notifications  payload  lists if the notificationEvent -n
                     flag is used together with monitor  -o  (or  -i)  varbind
                     options.

              If no monitor entries specify payload varbinds, then the setting
              of this directive is irrelevant.

       linkUpDownNotifications yes
              will configure the Event MIB tables to monitor the  ifTable  for
              network  interfaces  being  taken  up  or down, and triggering a
              linkUp or linkDown notification as appropriate.

              This is exactly equivalent to the configuration:

                     notificationEvent  linkUpTrap    linkUp   ifIndex ifAdminStatus ifOperStatus
                     notificationEvent  linkDownTrap  linkDown ifIndex ifAdminStatus ifOperStatus

                     monitor  -r 60 -e linkUpTrap   "Generate linkUp" ifOperStatus != 2
                     monitor  -r 60 -e linkDownTrap "Generate linkDown" ifOperStatus == 2

       defaultMonitors yes
              will configure the Event MIB tables to monitor the various  UCD-
              SNMP-MIB  tables  for  problems (as indicated by the appropriate
              xxErrFlag column objects).

              This is exactly equivalent to the configuration:

                     monitor   -o prNames -o prErrMessage "process table" prErrorFlag != 0
                     monitor   -o memErrorName -o memSwapErrorMsg "memory" memSwapError != 0
                     monitor   -o extNames -o extOutput "extTable" extResult != 0
                     monitor   -o dskPath -o dskErrorMsg "dskTable" dskErrorFlag != 0
                     monitor   -o laNames -o laErrMessage  "laTable" laErrorFlag != 0
                     monitor   -o fileName -o fileErrorMsg  "fileTable" fileErrorFlag != 0

       In both these latter cases, the snmpd.conf must also contain a  iquery-
       SecName  directive,  together with a corresponding createUser entry and
       suitable access control configuration.

   DisMan Schedule MIB
       The DisMan working group also produced a mechanism for scheduling  par-
       ticular  actions  (a  specified  SET  assignment) at given times.  This
       requires that the agent was built with support for the  disman/schedule
       module  (which  is  included as part of the default build configuration
       for the most recent distribution).

       There are three ways of specifying the scheduled action:

       repeat FREQUENCY OID = VALUE
              configures a SET assignment of the (integer) VALUE  to  the  MIB
              instance OID, to be run every FREQUENCY seconds.

       cron MINUTE HOUR DAY MONTH WEEKDAY  OID = VALUE
              configures  a  SET  assignment of the (integer) VALUE to the MIB
              instance OID, to be run at the times  specified  by  the  fields
              MINUTE to WEEKDAY.  These follow the same pattern as the equiva-
              lent crontab(5) fields.

              Note:  These fields should be specified as  a  (comma-separated)
                     list  of  numeric values.  Named values for the MONTH and
                     WEEKDAY fields are not supported, and neither  are  value
                     ranges. A wildcard match can be specified as '*'.

              The  DAY field can also accept negative values, to indicate days
              counting backwards from the end of the month.

       at MINUTE HOUR DAY MONTH WEEKDAY  OID = VALUE
              configures a one-shot SET assignment, to be  run  at  the  first
              matching time as specified by the fields MINUTE to WEEKDAY.  The
              interpretation of these fields is exactly the same  as  for  the
              cron directive.

EXTENDING AGENT FUNCTIONALITY
       One  of the first distinguishing features of the original UCD suite was
       the ability to extend the functionality of the  agent  -  not  just  by
       recompiling  with code for new MIB modules, but also by configuring the
       running agent to report additional information. There are a  number  of
       techniques to support this, including:

       o      running external commands (exec, extend, pass)

       o      loading new code dynamically (embedded perl, dlmod)

       o      communicating with other agents (proxy, SMUX, AgentX)

   Arbitrary Extension Commands
       The  earliest extension mechanism was the ability to run arbitrary com-
       mands or shell scripts. Such commands do not need to be aware  of  SNMP
       operations, or conform to any particular behaviour - the MIB structures
       are designed to accommodate any form of command output.   Use  of  this
       mechanism  requires  that the agent was built with support for the ucd-
       snmp/extensible and/or agent/extend modules (which are both included as
       part of the default build configuration).

       exec [MIBOID] NAME PROG ARGS

       sh [MIBOID] NAME PROG ARGS
              invoke  the  named  PROG with arguments of ARGS.  By default the
              exit status and first line of output from the  command  will  be
              reported via the extTable, discarding any additional output.

              Note:  Entries  in  this table appear in the order they are read
                     from the configuration file.  This means that adding  new
                     exec  (or  sh)  directives  and restarting the agent, may
                     affect the indexing of other entries.

              The PROG argument for exec directives must be a full path  to  a
              real  binary,  as it is executed via the exec() system call.  To
              invoke a shell script, use the sh directive instead.

              If MIBOID is specified, then the results will be rooted at  this
              point   in  the  OID  tree,  returning  the  exit  statement  as
              MIBOID.100.0 and the entire command  output  in  a  pseudo-table
              based at MIBNUM.101 - with one 'row' for each line of output.

              Note:  The  layout  of  this  "relocatable" form of exec (or sh)
                     output does not strictly  form  a  valid  MIB  structure.
                     This  mechanism  is  being  deprecated  -  please see the
                     extend directive (described below) instead.

              In either case, the exit statement and output will be cached for
              30s after the initial query.  This cache can be flushed by a SET
              request of the integer value 1  to  the  MIB  instance  version-
              ClearCache.0.

       execfix NAME PROG ARGS
              registers a command that can be invoked on demand - typically to
              respond to or fix errors  with  the  corresponding  exec  or  sh
              entry.   When  the extErrFix instance for a given NAMEd entry is
              set to the integer value of 1, this command will be called.

              Note:  This directive can only be used  in  combination  with  a
                     corresponding exec or sh directive, which must be defined
                     first.  Attempting to  define  an  unaccompanied  execfix
                     directive will fail.

       exec  and sh extensions can only be configured via the snmpd.conf file.
       They cannot be set up via SNMP SET requests.

       extend [MIBOID] NAME PROG ARGS
              works in a similar manner to the exec directive, but with a num-
              ber  of  improvements.  The MIB tables (nsExtendConfigTable etc)
              are indexed by the NAME token, so are unaffected by the order in
              which  entries are read from the configuration files.  There are
              two result tables - one  (nsExtendOutput1Table)  containing  the
              exit status, the first line and full output (as a single string)
              for each extend entry, and the other (nsExtendOutput2Table) con-
              taining the complete output as a series of separate lines.

              If MIBOID is specified, then the configuration and result tables
              will be rooted at this point in the OID tree, but are  otherwise
              structured in exactly the same way. This means that several sep-
              arate extend directives can specify the same MIBOID root,  with-
              out conflicting.

              The  exit  status  and output is cached for each entry individu-
              ally, and can be cleared (and the caching behaviour  configured)
              using the nsCacheTable.

       extendfix NAME PROG ARGS
              registers  a  command  that can be invoked on demand, by setting
              the appropriate nsExtendRunType instance to the  value  run-com-
              mand(3).  Unlike the equivalent execfix, this directive does not
              need to be paired with a corresponding  extend  entry,  and  can
              appear on its own.

       Both  extend  and  extendfix  directives can be configured dynamically,
       using SNMP SET requests to the NET-SNMP-EXTEND-MIB.

   MIB-Specific Extension Commands
       The first group of extension directives invoke arbitrary commands,  and
       rely  on  the  MIB  structure  (and management applications) having the
       flexibility to accommodate and interpret the output.  This is a  conve-
       nient  way  to make information available quickly and simply, but is of
       no use when implementing specific MIB objects, where the extension must
       conform  to  the  structure  of  the MIB (rather than vice versa).  The
       remaining extension mechanisms are all concerned with such MIB-specific
       situations  - starting with "pass-through" scripts.  Use of this mecha-
       nism requires that the agent  was  built  with  support  for  the  ucd-
       snmp/pass and ucd-snmp/pass_persist modules (which are both included as
       part of the default build configuration).

       pass [-p priority] MIBOID PROG
              will pass control of the subtree rooted at MIBOID to the  speci-
              fied  PROG  command.   GET  and GETNEXT requests for OIDs within
              this tree will trigger this command, called as:

                     PROG -g OID

                     PROG -n OID

              respectively, where OID is the requested OID.  The PROG  command
              should  return  the  response  varbind  as  three separate lines
              printed to stdout - the first line should  be  the  OID  of  the
              returned  value,  the second should be its TYPE (one of the text
              strings integer, gauge, counter, timeticks, ipaddress, objectid,
              or string ), and the third should be the value itself.

              If  the  command  cannot return an appropriate varbind - e.g the
              specified OID did not correspond to a valid instance for  a  GET
              request,  or  there  were no following instances for a GETNEXT -
              then it should exit without producing  any  output.   This  will
              result  in  an SNMP noSuchName error, or a noSuchInstance excep-
              tion.

                     Note:  The SMIv2 type counter64 and  SNMPv2  noSuchObject
                            exception are not supported.

              A SET request will result in the command being called as:

                     PROG -s OID TYPE VALUE

              where  TYPE  is  one  of the tokens listed above, indicating the
              type of the value passed as the third parameter.

              If the assignment is successful, the PROG  command  should  exit
              without  producing  any  output.  Errors  should be indicated by
              writing one of the strings not-writable, or wrong-type  to  std-
              out, and the agent will generate the appropriate error response.

                     Note:  The other SNMPv2 errors are not supported.

              In  either  case,  the  command should exit once it has finished
              processing.  Each request (and  each  varbind  within  a  single
              request) will trigger a separate invocation of the command.

              The  default  registration priority is 127.  This can be changed
              by supplying the optional -p flag, with lower priority registra-
              tions being used in preference to higher priority values.

       pass_persist [-p priority] MIBOID PROG
              will  also  pass  control of the subtree rooted at MIBOID to the
              specified PROG command.  However this command will  continue  to
              run  after  the initial request has been answered, so subsequent
              requests can be processed without the startup overheads.

              Upon initialization, PROG will be passed the string "PING\n"  on
              stdin, and should respond by printing "PONG\n" to stdout.

              For  GET  and GETNEXT requests, PROG will be passed two lines on
              stdin, the command (get or getnext) and the requested  OID.   It
              should  respond  by printing three lines to stdout - the OID for
              the result varbind, the TYPE and the VALUE itself -  exactly  as
              for  the  pass directive above.  If the command cannot return an
              appropriate varbind, it should print print  "NONE\n"  to  stdout
              (but continue running).

              For  SET requests, PROG will be passed three lines on stdin, the
              command (set) and the requested OID, followed by  the  type  and
              value (both on the same line).  If the assignment is successful,
              the command should print "DONE\n" to stdout.  Errors  should  be
              indicated  by  writing  one  of the strings not-writable, wrong-
              type, wrong-length, wrong-value or inconsistent-value to stdout,
              and  the agent will generate the appropriate error response.  In
              either case, the command should continue running.

              The registration priority can be changed using the  optional  -p
              flag, just as for the pass directive.

       pass  and  pass_persist  extensions  can  only  be  configured  via the
       snmpd.conf file.  They cannot be set up via SNMP SET requests.

   Embedded Perl Support
       Programs using the previous extension mechanisms can be written in  any
       convenient  programming  language  -  including perl, which is a common
       choice for pass-through extensions in particular.  However the Net-SNMP
       agent  also  includes  support for embedded perl technology (similar to
       mod_perl for the Apache web server).  This allows the agent  to  inter-
       pret perl scripts directly, thus avoiding the overhead of spawning pro-
       cesses and initializing the perl system when a request is received.

       Use of this mechanism requires that the agent was  built  with  support
       for the embedded perl mechanism, which is not part of the default build
       environment.  It  must  be  explicitly  included  by   specifying   the
       '--enable-embedded-perl'  option to the configure script when the pack-
       age is first built.

       If enabled, the following directives will be recognised:

       disablePerl true
              will turn off embedded perl support entirely (e.g. if there  are
              problems with the perl installation).

       perlInitFile FILE
              loads the specified initialisation file (if present) immediately
              before the first perl directive is parsed.   If  not  explicitly
              specified,  the  agent  will look for the default initialisation
              file /usr/share/snmp/snmp_perl.pl.

              The default initialisation file creates an instance  of  a  Net-
              SNMP::agent object - a variable $agent which can be used to reg-
              ister perl-based MIB handler routines.

       perl EXPRESSION
              evaluates the given expression.  This would typically register a
              handler  routine to be called when a section of the OID tree was
              requested:
                     perl use Data::Dumper;
                     perl sub myroutine  { print "got called: ",Dumper(@_),"\n"; }
                     perl $agent->register('mylink', '.1.3.6.1.8765', \&myroutine);

              This expression could also source an external file:
                     perl 'do /path/to/file.pl';

              or  perform  any  other  perl-based  processing  that  might  be
              required.

   Dynamically Loadable Modules
       Most  of  the MIBs supported by the Net-SNMP agent are implemented as C
       code modules, which were compiled and linked into the  agent  libraries
       when  the  suite was first built.  Such implementation modules can also
       be compiled independently and loaded into the running agent once it has
       started.   Use of this mechanism requires that the agent was built with
       support for the ucd-snmp/dlmod module (which is included as part of the
       default build configuration).

       dlmod NAME PATH
              will  load the shared object module from the file PATH (an abso-
              lute filename), and call the initialisation routine init_NAME.

              Note:  If the specified PATH is not a fully qualified  filename,
                     it  will  be interpreted relative to /usr/lib/snmp/dlmod,
                     and .so will be appended to the filename.

       This functionality can also be configured using SNMP  SET  requests  to
       the UCD-DLMOD-MIB.

   Proxy Support
       Another  mechanism  for  extending the functionality of the agent is to
       pass selected requests (or selected varbinds) to  another  SNMP  agent,
       which  can  be running on the same host (presumably listening on a dif-
       ferent port), or on a remote system.  This can be viewed either as  the
       main  agent delegating requests to the remote one, or acting as a proxy
       for it.  Use of this mechanism requires that the agent was  built  with
       support for the ucd-snmp/proxy module (which is included as part of the
       default build configuration).

       proxy [-Cn CONTEXTNAME] [SNMPCMD_ARGS] HOST OID [REMOTEOID]
              will pass any incoming requests under OID to the agent listening
              on  the  port  specified by the transport address HOST.  See the
              section LISTENING ADDRESSES in the snmpd(8) manual page for more
              information about the format of listening addresses.

              Note:  To  proxy  the entire MIB tree, use the OID .1.3 (not the
                     top-level .1)

       The SNMPCMD_ARGS should provide sufficient version  and  administrative
       information to generate a valid SNMP request (see snmpcmd(1)).

       Note:  The  proxied  request  will  not use the administrative settings
              from the original request.

       If a CONTEXTNAME is specified, this will register the proxy  delegation
       within  the  named context in the local agent.  Defining multiple proxy
       directives for the same OID but different contexts can be used to query
       several  remote agents through a single proxy, by specifying the appro-
       priate SNMPv3 context in the incoming request (or using  suitable  con-
       figured community strings - see the com2sec directive).

       Specifying  the  REMOID parameter will map the local MIB tree rooted at
       OID to an equivalent subtree rooted at REMOID on the remote agent.

   SMUX Sub-Agents
       The Net-SNMP agent supports the SMUX protocol (RFC 1227) to communicate
       with  SMUX-based  subagents  (such  as gated, zebra or quagga).  Use of
       this mechanism requires that the agent was built with support  for  the
       smux  module,  which  is not part of the default build environment, and
       must be explicitly included by specifying the '--with-mib-modules=smux'
       option to the configure script when the package is first built.

              Note:  This extension protocol has been officially deprecated in
                     favour of AgentX (see below).

       smuxpeer OID PASS
              will register a subtree for SMUX-based processing, to be authen-
              ticated using the password PASS.  If a subagent (or "peer") con-
              nects to the agent and registers this subtree then requests  for
              OIDs within it will be passed to that SMUX subagent for process-
              ing.

              A suitable entry for an OSPF  routing  daemon  (such  as  gated,
              zebra or quagga) might be something like
                     smuxpeer .1.3.6.1.2.1.14 ospf_pass

       smuxsocket <IPv4-address>
              defines  the IPv4 address for SMUX peers to communicate with the
              Net-SNMP agent.  The default is to listen on all IPv4 interfaces
              ("0.0.0.0"),   unless  the  package  has  been  configured  with
              "--enable-local-smux" at build time, which  causes  it  to  only
              listen  on  127.0.0.1  by  default. SMUX uses the well-known TCP
              port 199.

       Note the Net-SNMP agent will only operate as a SMUX  master  agent.  It
       does not support acting in a SMUX subagent role.

   AgentX Sub-Agents
       The Net-SNMP agent supports the AgentX protocol (RFC 2741) in both mas-
       ter and subagent roles.  Use of this mechanism requires that the  agent
       was built with support for the agentx module (which is included as part
       of the default build configuration), and  also  that  this  support  is
       explicitly enabled (e.g. via the snmpd.conf file).

       There  are two directives specifically relevant to running as an AgentX
       master agent:

       master agentx
              will enable the AgentX functionality  and  cause  the  agent  to
              start  listening  for  incoming  AgentX registrations.  This can
              also be activated by specifying the '-x' command-line option (to
              specify an alternative listening socket).

       agentXPerms SOCKPERMS [DIRPERMS [USER|UID [GROUP|GID]]]
              Defines  the permissions and ownership of the AgentX Unix Domain
              socket, and the parent directories of  this  socket.   SOCKPERMS
              and  DIRPERMS  must  be octal digits (see chmod(1) ). By default
              this socket will only be accessible to subagents which have  the
              same userid as the agent.

       There  is  one  directive specifically relevant to running as an AgentX
       sub-agent:

       agentXPingInterval NUM
              will make the subagent try and reconnect every  NUM  seconds  to
              the master if it ever becomes (or starts) disconnected.

       The  remaining  directives  are relevant to both AgentX master and sub-
       agents:

       agentXSocket [<transport-specifier>:]<transport-address>[,...]
              defines the address the master agent listens at, or the subagent
              should  connect  to.   The  default  is  the  Unix Domain socket
              "/var/agentx/master".  Another common alternative is  tcp:local-
              host:705.   See  the section LISTENING ADDRESSES in the snmpd(8)
              manual page for more information about the format of addresses.

              Note:  Specifying an AgentX socket does not automatically enable
                     AgentX   functionality   (unlike  the  '-x'  command-line
                     option).

       agentXTimeout NUM
              defines the timeout period (NUM seconds) for an AgentX  request.
              Default is 1 second.

       agentXRetries NUM
              defines the number of retries for an AgentX request.  Default is
              5 retries.

       net-snmp ships with both C and Perl APIs to  develop  your  own  AgentX
       subagent.

OTHER CONFIGURATION
       override [-rw] OID TYPE VALUE
              This  directive  allows  you to override a particular OID with a
              different value (and possibly a different type of  value).   The
              -rw  flag  will  allow  snmp  SETs to modify it's value as well.
              (note that if you're  overriding  original  functionality,  that
              functionality  will be entirely lost.  Thus SETS will do nothing
              more than modify the internal overridden value and will not per-
              form  any  of the original functionality intended to be provided
              by the MIB object.  It's an emulation only.)  An example:

                     override sysDescr.0 octet_str "my own sysDescr"

              That line will set the sysDescr.0 value to "my own sysDescr"  as
              well  as  make  it  modifiable  with SNMP SETs as well (which is
              actually illegal according to the MIB specifications).

              Note that care must be taken when using this.  For  example,  if
              you  try  to  override  a  property  of the 3rd interface in the
              ifTable with a new value and  later  the  numbering  within  the
              ifTable  changes it's index ordering you'll end up with problems
              and your modified value won't appear in the right place  in  the
              table.

              Valid   TYPEs  are:  integer,  uinteger,  octet_str,  object_id,
              counter, null (for gauges, use "uinteger"; for bit strings,  use
              "octet_str").  Note that setting an object to "null" effectively
              delete's it as being accessible.  No VALUE needs to be given  if
              the object type is null.

              More types should be available in the future.

       If you're trying to figure out aspects of the various mib modules (pos-
       sibly some that you've added yourself), the following may help you spit
       out  some  useful  debugging  information.   First off, please read the
       snmpd manual page on the -D flag.   Then  the  following  configuration
       snmpd.conf token, combined with the -D flag, can produce useful output:

       injectHandler HANDLER modulename
              This  will  insert new handlers into the section of the mib tree
              referenced by "modulename".  The types of handlers available for
              insertion are:

              stash_cache
                     Caches  information  returned from the lower level.  This
                     greatly help the performance of the agent, at the cost of
                     caching  the  data  such that its no longer "live" for 30
                     seconds (in this  future,  this  will  be  configurable).
                     Note  that  this means snmpd will use more memory as well
                     while the information is  cached.   Currently  this  only
                     works  for  handlers  registered using the table_iterator
                     support, which is only a few mib tables.  To use it,  you
                     need to make sure to install it before the table_iterator
                     point in the chain, so to do this:

                                       injectHandler  stash_cache   NAME   ta-
                     ble_iterator

                     If  you want a table to play with, try walking the nsMod-
                     uleTable with and without this injected.


              debug  Prints  out  lots  of  debugging  information  when   the
                     -Dhelper:debug flag is passed to the snmpd application.


              read_only
                     Forces turning off write support for the given module.


              serialize
                     If  a module is failing to handle multiple requests prop-
                     erly (using the new 5.0 module API), this will force  the
                     module to only receive one request at a time.


              bulk_to_next
                     If  a module registers to handle getbulk support, but for
                     some reason is failing to  implement  it  properly,  this
                     module  will  convert  all  getbulk  requests  to getnext
                     requests before the final module receives it.

       dontLogTCPWrappersConnects
              If the snmpd was compiled with  TCP  Wrapper  support,  it  logs
              every  connection  made  to the agent. This setting disables the
              log messages for accepted connections. Denied  connections  will
              still be logged.

       Figuring out module names
              To figure out which modules you can inject things into, run snm-
              pwalk on the nsModuleTable which will give a list of  all  named
              modules registered within the agent.

   Internal Data tables
       table NAME

       add_row NAME INDEX(ES) VALUE(S)

NOTES
       o      The Net-SNMP agent can be instructed to re-read the various con-
              figuration files, either via an snmpset assignment of integer(1)
              to                           UCD-SNMP-MIB::versionUpdateConfig.0
              (.1.3.6.1.4.1.2021.100.11.0), or by sending a kill  -HUP  signal
              to the agent process.

       o      All  directives  listed  with a value of "yes" actually accept a
              range of boolean values.  These will accept any  of  1,  yes  or
              true  to  enable the corresponding behaviour, or any of 0, no or
              false to disable it.  The default in each case is for  the  fea-
              ture  to  be  turned off, so these directives are typically only
              used to enable the appropriate behaviour.

EXAMPLE CONFIGURATION FILE
       See the EXAMPLE.CONF file in the top level source directory for a  more
       detailed example of how the above information is used in real examples.

FILES
       /etc/snmp/snmpd.conf

SEE ALSO
       snmpconf(1),  snmpusm(1), snmp.conf(5), snmp_config(5), snmpd(8), EXAM-
       PLE.conf, read_config(3).



4th Berkeley Distribution         08 Feb 2002                    SNMPD.CONF(5)