rdisc



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  ker-
       nel 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
       <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 capa-
       bility 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                   07 April 2005                        RDISC(8)

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