Technical data

Gateway Routing Daemon (GATED) Configuration Reference
A.14 Redirect Processing
• interface is the interface statement, which allows the enabling and disabling
of redirects on an interface-by-interface basis. See Section A.10.1 for the
description of the interface_list. The parameters are:
noredirects —Specifies that redirects received from the specified interface
will be ignored. The default is to accept redirects on all interfaces.
redirects — This is the default. This argument may be necessary when
noredirects are used on a wildcard interface descriptor.
• trustedgateways defines the list of gateways from which redirects will be
accepted. The gateway_list is a list of host names or addresses. By default,
all routers on the shared network(s) are trusted to supply redirects. But if
the trustedgateways clause is specified, only redirects from the gateways in
the list are accepted.
There are no redirect-specific tracing options. All nonerror messages are traced
under the normal class.
A.15 The Router Discovery Protocol
The Router Discovery Protocol is an IETF standard protocol used to inform hosts
of the existence of routers. It is intended to be used instead of having hosts
wiretap routing protocols such as RIP. It is used in place of, or in addition to
statically configured default routes in hosts.
The protocol is split into to portions, the server portion which runs on routers,
and the client portion that runs on hosts. GATED treats these much like two
separate protocols, only one of which may be enabled at a time.
A.15.1 The Router Discovery Server
The Router Discovery Server runs on routers and announces their existence
to hosts. It does this by periodically multicasting or broadcasting a Router
Advertisement to each interface on which it is enabled. These Router
Advertisements contain a list of all the routers addresses on a given interface and
their preference for use as a default router.
Initially these Router Advertisements occur every few seconds, then fall back to
every few minutes. In addition, a host may send a Router Solicitation to which
the router will respond with a unicast Router Advertisement (unless a multicast
or broadcast advertisement is due momentarily).
Each Router Advertisement contains a Advertisement Lifetime field, which
indicates for how long the advertised addresses are valid. This lifetime is
configured such that another Router Advertisement will be sent before the
lifetime has expired. A lifetime of zero is used to indicate that one or more
addresses are no longer valid.
On systems supporting IP multicasting, the Router Advertisements are by
default sent to the all-hosts multicast address 224.0.0.1. However, the use of
broadcast may be specified. When Router Advertisements are being sent to the
all-hosts multicast address, or an interface is configured for the limited-broadcast
address 255.255.255.255, all IP addresses configured on the physical interface
are included in the Router Advertisement. When the Router advertisements are
being sent to a net or subnet broadcast, only the address associated with that net
or subnet is included.
A–20 Gateway Routing Daemon (GATED) Configuration Reference