rdisc - network router discovery daemon
[-T max_interval] [send_address]
rdisc implements client side of the ICMP Internet Router Discovery
Protocol (IRDP). rdisc is invoked at boot time to populate the network
routing tables with default routes.
rdisc listens on the ALL_HOSTS (188.8.131.52) multicast
address (or receive_address if it is provided) 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 (184.108.40.206) multicast address (or send_address if it is
provided) when it is started.
A timer is associated with each router address and the address
will no longer be considered for inclusion in 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 received
advertise message has a preference of maximum negative.
Server side of router discovery protocol is supported by Cisco IOS
and by any more or less complete UNIX routing daemon, for example
gated. If compiled with ENABLE_RDISC_SERVER, rdisc can act as
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
Opposite to -a, i.e. install only router with the
best preference value. This is the default behaviour.
Send debugging messages to syslog.
Keep rdisc running in the background even if no
routers are found. Normally rdisc gives up if it has not received any
advertise message after soliciting three times. In this case it exits
with a non-zero exit code. If -f is not specified in the first form
then -s must be specified.
Responder mode, available only if compiled with
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.
Set preference in advertisement messages. Available only
with -r option.
Set maximum advertisement interval in seconds. Default is
600. Available only with -r option.
Test mode. Do not go to background.
Be verbose and send lots of debugging messages to
Print version and exit.
This program was developed by Sun Microsystems (see copyright notice in source
file). It was ported to Linux by Alexey Kuznetsov
RFC1256 ICMP Router Discovery Messages. S. Deering, Ed.. September 1991.
rdisc requires CAP_NET_RAW to listen and send ICMP messages and
capability CAP_NET_ADMIN to update routing tables.
rdisc is part of iputils package.