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



NAME
       rdisc - network router discovery daemon

SYNOPSIS
       rdisc [ -abdfstvV]  [ send_address]  [ receive_address]


DESCRIPTION
       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 (224.0.0.1) multicast address (or receive_address provided it is given) for  ROUTER_ADVER-
       TISE  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 (224.0.0.2) 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.

OPTIONS
       -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 mes-
              sage 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.

       -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.

       -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
       This program was developed by Sun Microsystems (see copyright notice in source file). It was ported to  Linux  by  Alexey
       Kuznetsov <kuznetATms2.ru>.  It is now maintained by YOSHIFUJI Hideaki <yoshfujiATskbuff.net>.

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

REFERENCES
       Deering,  S.E.,ed  "ICMP  Router Discovery Messages", RFC1256, Network Information Center, SRI International, Menlo Park,
       Calif., September 1991.

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

AVAILABILITY
       rdisc   is   part   of   iputils   package   and   the   latest   versions   are    available   in   source    form    at
       http://www.skbuff.net/iputils/iputils-current.tar.bz2.



iputils-100418                                            13 July 2010                                                  RDISC(8)