Technical data

Gateway Routing Daemon (GATED) Configuration Reference
A.15 The Router Discovery Protocol
multicast , which specifies that the given addresses should only be
included in a multicast Router Advertisement. If the system does not
support IP multicasting the addresses will not be included. If the system
supports IP multicasting, the default is to include the addresses in
a multicast Router Advertisement if the given interface supports IP
multicasting, if not the addresses will be included in a broadcast Router
Advertisement.
preference , which specifies the preferability of the addresses as a default
router address, relative to other router addresses on the same subnet. A
32-bit, signed, twos-complement integer, with higher values meaning more
preferable. Note that hex 80000000 may only be specified as ineligible.
The default is 0.
ineligible , which specifies that the given addresses will be assigned a
preference of (hex 80000000) which means that it is not eligible to be the
default route for any hosts.
This is useful when the addresses should not be used as a default route,
but are given as the next hop in an ICMP redirect. This allows the hosts
to verify that the given addresses are up and available.
A.15.2 The Router Discovery Client
A host listens for Router Advertisements via the all-hosts multicast address
(224.0.0.2), If IP multicasting is available and enabled, or on the interface’s
broadcast address. When starting up, or when reconfigured, a host may send
a few Router Solicitations to the all-routers multicast address, 224.0.0.2, or the
interface’s broadcast address.
When a Router Advertisement with non-zero lifetime is received, the host installs
a default route to each of the advertised addresses. If the preference
ineligible ,
or the address is not on an attached interface, the route is marked unusable
but retained. If the preference is usable, the metric is set as a function of the
preference such that the route with the best preference is used. If more than one
address with the same preference is received, the one with the lowest IP address
will be used. These default routes are not exportable to other protocols.
When a Router Advertisement with a zero lifetime is received, the host deletes all
routes with next-hop addresses learned from that router. In addition, any routers
learned from ICMP redirects pointing to these addresses will be deleted. The
same will happen when a Router Advertisement is not received to refresh these
routes before the lifetime expires.
The Router Discovery Client syntax is as follows:
routerdiscovery client yes | no | on | off [ {
traceoptions trace_options ;
preference preference ;
interface interface_list
[ enable ] | [ disable ]
[ broadcast ] | [ multicast ]
[ quiet ] | [ solicit ]
;
}];
In the Router Discovery Client statement:
• traceoptions specifies the tracing options for OSPF (see Section A.15.3).
A–22 Gateway Routing Daemon (GATED) Configuration Reference