"in.rdisc" "" "\fLin.rdisc\fP \(em ICMP router discovery daemon"
"Internet" "ICMP router discovery daemon" "" "ICMP router discovery daemon \(em \fLin.rdisc\fP"
"Internet Control Message Protocol" "See ICMP"
"ICMP" "router discovery daemon" "" "router discovery daemon \(em \fLin.rdisc\fP"
\f4in.rdisc\f1
implements the
router discover protocol.
The first form of the command is used on hosts and the
second form is used on routers.
On a host \f4in.rdisc\f1 is invoked at
boot time to populate the network routing tables with default routes.
On a router it is also invoked at boot time in order to start
advertising the router to all the hosts.
On a host \f4in.rdisc\f1
listens on the \f4ALL_HOSTS\f1 (224.0.0.1) multicast address
for \f4ROUTER_ADVERTISE\f1 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, \f4in.rdisc\f1 can avoid waiting for routers to announce
themselves by sending out a few \f4ROUTER_SOLICITATION\f1 messages
to the \f4ALL_ROUTERS\f1 (224.0.0.2) multicast address 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.
When
\f4in.rdisc\f1
is started on a router, it uses the
\f4SIOCGIFCONF\f1
ioctl (2)
to find the interfaces configured into the system and it starts
listening on the \f4ALL_ROUTERS\f1 multicast address on all the interfaces
that support multicast.
It sends out
advertise
messages to the \f4ALL_HOSTS\f1 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 \f4in.rdisc\f1
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.
1i
