1RDISC(8) System Manager's Manual: iputils RDISC(8)
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6 rdisc - network router discovery daemon
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9 rdisc [ -abdfstvV] [ send_address] [ receive_address]
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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.
16 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.
24 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.
29 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.
36 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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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.
45 -b Opposite to -a, i.e. install only router with the best prefer‐
47 ence value. It is default behaviour.
48 -d Send debugging messages to syslog.
50 -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.
56 -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.
61 -t Test mode. Do not go to background.
63 -v Be verbose i.e. send lots of debugging messages to syslog.
65 -V Print version and exit.
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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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75 icmp(7), inet(7), ping(8).
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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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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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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.
90iputils-071127 22 March 2017 RDISC(8)