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dhcp_network(4)                  File Formats                  dhcp_network(4)



NAME
       dhcp_network - DHCP network tables

DESCRIPTION
       The  Dynamic Host Configuration Protocol (DHCP) network tables are used
       to map the client identifiers of DHCP clients to IP addresses  and  the
       associated  configuration  parameters of that address. One DHCP network
       table exists for each network served by the DHCP server, and each table
       is named using the network's IP address. There is no table or file with
       the name dhcp_network.

       The DHCP network tables can exist as  ASCII  text  files,  binary  text
       files, or NIS+ tables, depending on the data store used. Since the for-
       mat of the file could change, the preferred method of managing the DHCP
       network tables is through the use of dhcpmgr(1M) or the pntadm(1M) com-
       mand.

       The dhcp_network file  is  used  as  a  policy  mechanism  for  whether
       in.dhcpd(1M) leases addresses on a given network. If the DHCP server is
       not serving leases or information to a  network,  there  should  be  no
       dhcp_network  file for that network. To set the DHCP server in informa-
       tional mode, where it responds to INFORM messages but  does  not  lease
       addresses  on  that network, create an empty dhcp_network file for that
       network. For normal operations,  where  the  DHCP  server  both  leases
       addresses  and  responds  to INFORM packets, create a dhcp_network file
       using  dhcpmgr(1M)  or  pntadm(1M)  and  populate  it   with   leasable
       addresses.

       The  format  of the records in a DHCP network table depends on the data
       store used to maintain the table. However, an entry in a  DHCP  network
       table must contain the following fields:

       Client_ID       The  client  identifier  field,  Client_ID, is an ASCII
                       hexadecimal representation of the unique  octet  string
                       value  of  the  DHCP Client Identifier Option (code 61)
                       which identifies a DHCP client. In the absence  of  the
                       DHCP Client Identifier Option, the DHCP client is iden-
                       tified using the form given below  for  BOOTP  clients.
                       The  number of characters in this field must be an even
                       number, with a maximum length of 64  characters.  Valid
                       characters are 0 - 9 and A-F. Entries with values of 00
                       are freely available for dynamic allocation to request-
                       ing  clients.  BOOTP clients are identified by the con-
                       catenation of the network's hardware type  (as  defined
                       by   RFC  1340,  titled  "Assigned  Numbers")  and  the
                       client's hardware address. For example,  the  following
                       BOOTP  client  has a hardware type of '01' (10mb ether-
                       net) and a hardware address of 8:0:20:11:12:b7, so  its
                       client identifier would be: 010800201112B7



       Flags           The  Flags  field is a decimal value, the bit fields of
                       which can have a combination of the following values:

                       1 (PERMANENT)

                           Evaluation of the Lease field is turned off  (lease
                           is  permanent).  If this bit is not set, Evaluation
                           of the Lease field is  enabled  and  the  Lease  is
                           DYNAMIC.




                       2 (MANUAL)

                           This  entry  has a manual client ID binding (cannot
                           be reclaimed by DHCP server). Client  will  not  be
                           allocated another address.



                       4 (UNUSABLE)

                           When set, this value means that either through ICMP
                           echo or client DECLINE, this address has been found
                           to  be  unusable.  Can  also be used by the network
                           administrator to  prevent  a  certain  client  from
                           booting,  if  used  in  conjunction with the MANUAL
                           flag.



                       8 (BOOTP)

                           This entry is  reserved  for  allocation  to  BOOTP
                           clients only.




       Client_IP       The  Client_IP  field  holds  the  IP  address for this
                       entry. This value must be unique in the database.



       Server_IP       This field holds the IP  address  of  the  DHCP  server
                       which  owns this client IP address, and thus is respon-
                       sible for initial allocation to a requesting client. On
                       a  multi-homed DHCP server, this IP address must be the
                       first address returned by gethostbyname(3NSL).



       Lease           This numeric field holds  the  entry's  absolute  lease
                       expiration  time,  and  is  in seconds since January 1,
                       1970. It can be decimal, or hexadecimal (if 0x prefixes
                       number).  The special value -1 is used to denote a per-
                       manent lease.



       Macro           This ASCII text field contains the dhcptab  macro  name
                       used  to  look up this entry's configuration parameters
                       in the dhcptab(4) database.



       Comment         This ASCII text field contains an optional comment.



   TREATISE ON LEASES
       This section describes how the DHCP/BOOTP server calculates a  client's
       configuration  lease  using information contained in the dhcptab(4) and
       DHCP network tables. The server consults the LeaseTim and LeaseNeg sym-
       bols  in  the  dhcptab, and the Flags and Lease fields of the chosen IP
       address record in the DHCP network table.

       The server first examines the Flags field for the identified DHCP  net-
       work table record. If the PERMANENT flag is on, then the client's lease
       is considered permanent.

       If the PERMANENT flag is not on, the  server  checks  if  the  client's
       lease as represented by the Lease field in the network table record has
       expired. If the lease is not expired, the server checks if  the  client
       has  requested  a  new  lease.   If  the  LeaseNeg  symbol has not been
       included  in  the  client's  dhcptab  parameters,  then  the   client's
       requested  lease  extension  is ignored, and the lease is set to be the
       time remaining as shown by the Lease field. If the LeaseNeg symbol  has
       been  included,  then  the server will extend the client's lease to the
       value it requested if this requested lease is less than or equal to the
       current time plus the value of the client's LeaseTim dhcptab parameter.

       If the client's requested lease is greater than policy allows (value of
       LeaseTim), then the client is given a lease equal to the  current  time
       plus  the  value  of LeaseTim. If LeaseTim is not set, then the default
       LeaseTim value is one hour.

       For more information about the dhcptab symbols, see dhcptab(4).

ATTRIBUTES
       See attributes(5) for a description of the following attribute:


       tab()    allbox;    cw(2.750000i)|     cw(2.750000i)     lw(2.750000i)|
       lw(2.750000i).   ATTRIBUTE  TYPEATTRIBUTE  VALUE  AvailabilitySUNWdhcsu
       Interface StabilityEvolving


SEE ALSO
       dhcpconfig(1M),  dhcpmgr(1M),  dhtadm(1M),  in.dhcpd(1M),   pntadm(1M),
       dhcptab(4), dhcp(5), dhcp_modules(5), attributes(5)

       Solaris DHCP Service Developer's Guide

       System Administration Guide: IP Services

       Reynolds,  J.  and  J.  Postel,  Assigned  Numbers,  STD  2,  RFC 1340,
       USC/Information Sciences Institute, July 1992.



SunOS 5.10                        5 Mar 2004                   dhcp_network(4)