RDISC(8)              System Manager's Manual: iputils              RDISC(8)

NAME         top

       rdisc - network router discovery daemon

SYNOPSIS         top

       rdisc [-abdfrstvV] [-p preference] [-T max_interval] [send_address]

DESCRIPTION         top

       rdisc implements client side of the ICMP router discover protocol.
       rdisc is invoked at boot time to populate the network routing tables
       with default routes.

       rdisc listens on the ALL_HOSTS ( multicast address (or
       receive_address provided it is given) for ROUTER_ADVERTISE messages
       from routers. The received messages are handled by first ignoring
       those listed router addresses with which the host does not share a
       network. Among the remaining addresses the ones with the highest
       preference are selected as default routers and a default route is
       entered in the kernel routing table for each one of them.

       Optionally, rdisc can avoid waiting for routers to announce
       themselves by sending out a few ROUTER_SOLICITATION messages to the
       ALL_ROUTERS ( multicast address (or send_address provided
       it is given) when it is started.

       A timer is associated with each router address and the address will
       no longer be considered for inclusion in the the routing tables if
       the timer expires before a new advertise message is received from the
       router.  The address will also be excluded from consideration if the
       host receives an advertise message with the preference being
       maximally negative.

       Server side of router discovery protocol is supported by Cisco IOS
       and by any more or less complete UNIX routing daemon, f.e gated.  Or,
       rdisc can act as responder, if compiled with -DRDISC_SERVER.

OPTIONS         top

       -a     Accept all routers independently of the preference they have
              in their advertise messages.  Normally rdisc only accepts (and
              enters in the kernel routing tables) the router or routers
              with the highest preference.

       -b     Opposite to -a, i.e. install only router with the best
              preference value. It is default behaviour.

       -d     Send debugging messages to syslog.

       -f     Run rdisc forever even if no routers are found.  Normally
              rdisc gives up if it has not received any advertise message
              after after soliciting three times, in which case it exits
              with a non-zero exit code.  If -f is not specified in the
              first form then -s must be specified.

       -r     Responder mode, available only if compiled with

       -s     Send three solicitation messages initially to quickly discover
              the routers when the system is booted.  When -s is specified
              rdisc exits with a non-zero exit code if it can not find any
              routers.  This can be overridden with the -f option.

       -p preference
              Set preference in advertisement.  Available only with -r

       -T max_interval
              Set maximum advertisement interval in seconds.  Default is 600
              secs.  Available only with -r option.

       -t     Test mode. Do not go to background.

       -v     Be verbose i.e. send lots of debugging messages to syslog.

       -V     Print version and exit.

HISTORY         top

       This program was developed by Sun Microsystems (see copyright notice
       in source file). It was ported to Linux by Alexey Kuznetsov
       <>.  It is now maintained by YOSHIFUJI Hideaki

SEE ALSO         top

       icmp(7), inet(7), ping(8).

REFERENCES         top

       Deering, S.E.,ed "ICMP Router Discovery Messages", RFC1256, Network
       Information Center, SRI International, Menlo Park, Calif., September

SECURITY         top

       rdisc requires CAP_NET_RAW to listen and send ICMP messages and
       capability CAP_NET_ADMIN to update routing tables.

AVAILABILITY         top

       rdisc is part of iputils package and the latest versions are
       available in source form at

COLOPHON         top

       This page is part of the iputils (IP utilities) project.  Information
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iputils-151218                  05 July 2017                        RDISC(8)