IN.RDISC(8) Maintenance Procedures IN.RDISC(8)


in.rdisc, rdisc - network router discovery daemon


/usr/sbin/in.rdisc [-a] [-f] [-s] [send-address] [receive-address]

/usr/sbin/in.rdisc -r [-p preference] [-T interval]
[send-address] [receive-address]


in.rdisc remains part of the software distribution of the Solaris
Operating Environment. It is, however, not used by default. in.routed(8)
includes the functionality provided by in.rdisc. See routeadm(8) for
details of how to specify the IPV4 routing daemon.

in.rdisc implements the ICMP router discovery protocol. The first form of
the command is used on hosts and the second form is used on routers.

in.rdisc can be invoked in either the first form (host mode) or second
form (router mode).

On a host, in.rdisc populates the network routing tables with default
routes. On a router, advertises the router to all the hosts.

in.rdisc is managed by the service management facility (SMF), by means of
the service identifier:


Host (First Form)
On a host, in.rdisc listens on the ALL_HOSTS ( multicast
address 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

Optionally, in.rdisc can avoid waiting for routers to announce themselves
by sending out a few ROUTER_SOLICITATION messages to the ALL_ROUTERS
( multicast address when it is started.

A timer is associated with each router address. 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 host receives an
advertise message with the preference being maximally negative or with a
lifetime of zero.

Router (Second Form)
When in.rdisc is started on a router, it uses the SIOCGIFCONF ioctl(2) to
find the interfaces configured into the system and it starts listening on
the ALL_ROUTERS multicast address on all the interfaces that support
multicast. It sends out advertise messages to the ALL_HOSTS multicast
address advertising all its IP addresses. A few initial advertise
messages are sent out during the first 30 seconds and after that it will
transmit advertise messages approximately every 600 seconds.

When in.rdisc receives a solicitation message, it sends an advertise
message to the host that sent the solicitation message.

When in.rdisc is terminated by a signal, it sends out an advertise
message with the preference being maximally negative.


Supported options and equivalent SMF service properties are listed below.
SMF service properties are set using a command of the form:

# routeadm -m rdisc:default key=value

Accept all routers independent of the preference they
have in their advertise messages. Normally, in.rdisc
only accepts (and enters in the kernel routing tables)
the router or routers with the highest preference. Use
of this option is equivalent to setting the accept_all
property to true.

Run in.rdisc forever even if no routers are found.
Normally, in.rdisc gives up if it has not received any
advertise message 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.
For SMF execution, this option is required.

Act as a router, rather than a host. Use of this option
is equivalent to setting the act_as_router property to

Send three solicitation messages initially to quickly
discover the routers when the system is booted. When -s
is specified, in.rdisc exits with a non-zero exit code
if it can not find any routers. This can be overridden
with the -f option. This option is not compatible with
SMF execution and is not supported for the rdisc

-p preference
Set the preference transmitted in the solicitation
messages. The default is zero. Use of this option is
equivalent to setting the preference property.

-T interval
Set the interval between transmitting the advertise
messages. The default time is 600 seconds. Use of this
option is equivalent to setting the transmit_interval

The send-address and receive-address daemon options can be set by means
of the send_address and receive_address properties.


ioctl(2), icmp(4P), inet(4P), gateways(5), attributes(7), smf(7),
in.routed(8), routeadm(8), svcadm(8)

Deering, S.E., editor, ICMP Router Discovery Messages, RFC 1256, Network
Information Center, SRI International, Menlo Park, California, September

November 9, 2006 IN.RDISC(8)