1RDISC(8)               System Manager's Manual: iputils               RDISC(8)
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NAME

6       rdisc - network router discovery daemon
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SYNOPSIS

9       rdisc [ -abdfstvV]  [ send_address]  [ receive_address]
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DESCRIPTION

13       rdisc  implements  client  side  of  the ICMP router discover protocol.
14       rdisc is invoked at boot time to populate the  network  routing  tables
15       with default routes.
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17       rdisc  listens  on  the  ALL_HOSTS  (224.0.0.1)  multicast  address (or
18       receive_address provided it is  given)  for  ROUTER_ADVERTISE  messages
19       from routers. The received messages are handled by first ignoring those
20       listed router addresses with which the host does not share  a  network.
21       Among  the remaining addresses the ones with the highest preference are
22       selected as default routers and a default route is entered in the  ker‐
23       nel routing table for each one of them.
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25       Optionally,  rdisc can avoid waiting for routers to announce themselves
26       by sending out a few ROUTER_SOLICITATION messages  to  the  ALL_ROUTERS
27       (224.0.0.2)  multicast  address  (or send_address provided it is given)
28       when it is started.
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30       A timer is associated with each router address and the address will  no
31       longer  be  considered  for  inclusion in the the routing tables if the
32       timer expires before a new  advertise  message  is  received  from  the
33       router.   The  address  will also be excluded from consideration if the
34       host receives an advertise message with the preference being  maximally
35       negative.
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37       Server  side of router discovery protocol is supported by Cisco IOS and
38       by any more or less complete UNIX routing daemon, f.e gated.
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OPTIONS

41       -a     Accept all routers independently of the preference they have  in
42              their  advertise  messages.   Normally  rdisc  only accepts (and
43              enters in the kernel routing tables) the router or routers  with
44              the highest preference.
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46       -b     Opposite  to  -a, i.e. install only router with the best prefer‐
47              ence value. It is default behaviour.
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49       -d     Send debugging messages to syslog.
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51       -f     Run rdisc forever even if no routers are found.  Normally  rdisc
52              gives  up  if  it  has  not received any advertise message after
53              after soliciting three times, in which case it exits with a non-
54              zero  exit  code.  If -f is not specified in the first form then
55              -s must be specified.
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57       -s     Send three solicitation messages initially to  quickly  discover
58              the  routers  when  the  system is booted.  When -s is specified
59              rdisc exits with a non-zero exit code if it  can  not  find  any
60              routers.  This can be overridden with the -f option.
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62       -t     Test mode. Do not go to background.
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64       -v     Be verbose i.e. send lots of debugging messages to syslog.
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66       -V     Print version and exit.
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HISTORY

69       This program was developed by Sun Microsystems (see copyright notice in
70       source  file).  It  was   ported   to   Linux   by   Alexey   Kuznetsov
71       <kuznet@ms2.inr.ac.ru>.   It  is  now  maintained  by YOSHIFUJI Hideaki
72       <yoshfuji@skbuff.net>.
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SEE ALSO

75       icmp(7), inet(7), ping(8).
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REFERENCES

78       Deering, S.E.,ed "ICMP Router  Discovery  Messages",  RFC1256,  Network
79       Information  Center,  SRI  International, Menlo Park, Calif., September
80       1991.
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SECURITY

83       rdisc requires CAP_NET_RAWIO to listen and send ICMP messages and capa‐
84       bility CAP_NET_ADMIN to update routing tables.
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AVAILABILITY

87       rdisc is part of iputils package and the latest versions are  available
88       in   source    form    at    http://www.skbuff.net/iputils/iputils-cur
89       rent.tar.bz2.
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93iputils-071127                   22 March 2017                        RDISC(8)
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