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_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
       (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 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.

       -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
       <kuznet@ms2.inr.ac.ru>.

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  for  anonymous  ftp  ftp://ftp.inr.ac.ru/ip-rout-
       ing/iputils-current.tar.gz.

iputils-020927							 27 September 2002							  RDISC(8)