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 pref-
       erence 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 prefer-
	      ence 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
       .

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   avail-
       able  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)

UNIX/Linux commands referenced on this page:

1. at
2. time
3. addresses
4. which
5. host
6. as
7. route
8. more
9. less
10. install
11. find
12. ftp