RDISC(8)                           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 ENABLE_RDISC_SERVER.

OPTIONS         top

           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.

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

           Send debugging messages to syslog.

           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.

           Responder mode, available only if compiled with

           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 option.

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

           Test mode. Do not go to background.

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

           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

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.

COLOPHON         top

       This page is part of the iputils (IP utilities) project.  Information
       about the project can be found at ⟨⟩.
       If you have a bug report for this manual page, send it to,  This page was obtained
       from the project's upstream Git repository
       ⟨⟩ on 2019-05-09.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2019-04-19.)  If you discover any rendering problems in
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       more up-to-date source for the page, or you have corrections or
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       of the original manual page), send a mail to

iputils s20190324                                                   RDISC(8)

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