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ROUTED(8C)                                                          ROUTED(8C)

       routed, in.routed - network routing daemon

       /usr/etc/in.routed [ -qstv ] [ 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() (see  ioctl(2))
       to  find those directly connected interfaces configured into the system
       and marked "up" (the software loopback interface is ignored).  If  mul-
       tiple interfaces are present, it is assumed the host will forward pack-
       ets 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.

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

       o      No  routing  table  entry  exists for the destination network or
              host, and the metric indicates the  destination  is  "reachable"
              (that is, the hop count is not infinite).

       o      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.

       o      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.

       o      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.

       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 (that is, 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:

              <&lt;  net  | host >&gt; filename1 gateway filename2 metric value <&lt; pas-
              sive | active >&gt;

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

       filename1  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).

       filename2  is  the  name  or  address  of the gateway to which messages
       should be forwarded.

       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).

       -s     Force routed to supply routing information whether it is  acting
              as an internetwork router or not.

       -q     Opposite of the -s option.

       -t     All packets sent or received are printed on the standard output.
              In addition, routed will not divorce itself from the controlling
              terminal  so  that  interrupts  from  the keyboard will kill the

       -v     Allow a logfile to be created showing the changes  made  to  the
              routing tables with a timestamp.

              Specify  a file in which routed records any changes to the rout-
              ing tables and a history of recent messages  sent  and  received
              which are related to the changed route.

       /etc/gateways       for distant gateways

       ioctl(2), inet(3N), udp(4P)

       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.

                               9 September 1987                     ROUTED(8C)