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ROUTED(8C)                                                          ROUTED(8C)

       routed - network routing daemon

       /etc/routed [ -s ] [ -q ] [ -t ] [ logfile ]

       Routed  is  invoked  at boot time to manage the network routing tables.
       The routing daemon uses a variant of the Xerox NS  Routing  Information
       Protocol in maintaining up to date kernel routing table entries.

       In  normal operation routed listens on udp(4P) socket 520 (decimal) for
       routing information packets.  If the host is an internetwork router, it
       periodically supplies copies of its routing tables to any directly con-
       nected hosts and networks.

       When routed is started, it uses the SIOCGIFCONF  ioctl  to  find  those
       directly  connected  interfaces  configured  into the system and marked
       ``up'' (the software  loopback  interface  is  ignored).   If  multiple
       interfaces  are  present,  it  is assumed the host will forward packets
       between networks.  Routed then  transmits  a  request  packet  on  each
       interface  (using  a broadcast packet if the interface supports it) and
       enters a loop, listening for request and response  packets  from  other

       When  a  request packet is received, routed formulates a reply based on
       the information maintained in its internal tables.  The response packet
       generated  contains  a  list  of known routes, each marked with a ``hop
       count'' metric (a count of 16, or greater, is considered ``infinite'').
       The  metric associated with each route returned provides a metric rela-
       tive to the sender.

       Response packets received by routed are  used  to  update  the  routing
       tables if one of the following conditions is satisfied:

       (1)    No  routing  table  entry  exists for the destination network or
              host, and the metric indicates the destination is  ``reachable''
              (i.e. the hop count is not infinite).

       (2)    The  source  host of the packet is the same as the router in the
              existing routing table entry.  That is, updated  information  is
              being  received  from the very internetwork router through which
              packets for the destination are being routed.

       (3)    The existing entry in the routing table has not been updated for
              some  time  (defined to be 90 seconds) and the route is at least
              as cost effective as the current route.

       (4)    The new route describes a shorter route to the destination  than
              the  one  currently  stored in the routing tables; the metric of
              the new route is compared against the one stored in the table to
              decide this.

       When  an  update  is applied, routed records the change in its internal
       tables and generates a response packet to all directly connected  hosts
       and  networks.   Routed  waits  a short period of time (no more than 30
       seconds) before modifying the kernel's routing tables to allow possible
       unstable situations to settle.

       In  addition  to  processing incoming packets, routed also periodically
       checks the routing table entries.  If an entry has not been updated for
       3  minutes,  the entry's metric is set to infinity and marked for dele-
       tion.  Deletions are delayed an additional 60  seconds  to  insure  the
       invalidation is propagated throughout the internet.

       Hosts  acting as internetwork routers gratuitously supply their routing
       tables every 30 seconds to all directly connected hosts and networks.

       Supplying the -s option forces routed  to  supply  routing  information
       whether  it  is acting as an internetwork router or not.  The -q option
       is the opposite of the -s option.  If the -t option is  specified,  all
       packets  sent or received are printed on the standard output.  In addi-
       tion, routed will not divorce itself from the controlling  terminal  so
       that  interrupts  from  the  keyboard will kill the process.  Any other
       argument supplied is interpreted as the name of file in which  routed's
       actions  should  be  logged.   This  log contains information about any
       changes to the routing tables and a history of recent messages sent and
       received which are related to the changed route.

       In  addition  to  the  facilities  described above, routed supports the
       notion of ``distant'' passive and  active  gateways.   When  routed  is
       started  up, it reads the file /etc/gateways to find gateways which may
       not be identified using the SIOGIFCONF ioctl.   Gateways  specified  in
       this  manner  should  be  marked  passive  if  they are not expected to
       exchange routing information, while gateways marked  active  should  be
       willing  to  exchange  routing  information  (i.e.   they should have a
       routed process running on the machine).   Passive  gateways  are  main-
       tained  in  the  routing tables forever and information regarding their
       existence is included in any routing information  transmitted.   Active
       gateways  are  treated equally to network interfaces.  Routing informa-
       tion is distributed to the gateway and if  no  routing  information  is
       received for a period of the time, the associated route is deleted.

       The  /etc/gateways  is comprised of a series of lines, each in the fol-
       lowing format:

       < net | host > name1 gateway name2 metric value < passive | active >

       The net or host keyword indicates if the route is to a network or  spe-
       cific host.

       Name1  is  the  name of the destination network or host.  This may be a
       symbolic name located in /etc/networks or /etc/hosts,  or  an  Internet
       address specified in ``dot'' notation; see inet(3N).

       Name2 is the name or address of the gateway to which messages should be

       Value is a metric indicating the hop count to the destination  host  or

       The  keyword  passive  or  active  indicates  if  the gateway should be
       treated as passive or active (as described above).

       /etc/gateways  for distant gateways

       ``Internet Transport Protocols'', XSIS 028112, Xerox System Integration

       The  kernel's  routing tables may not correspond to those of routed for
       short periods of time while processes utilizing existing  routes  exit;
       the only remedy for this is to place the routing process in the kernel.

       Routed  should listen to intelligent interfaces, such as an IMP, and to
       error protocols, such as ICMP, to gather more information.

4th Berkeley Distribution       3 February 1983                     ROUTED(8C)