Installing and Administering Internet Services

282 Chapter 8
Configuring gated
Configuring the Router Discovery Protocol (RDP)
Configuring the Router Discovery
Protocol (RDP)
The Router Discovery Protocol (RDP) is a standard protocol that is used
to inform hosts of the presence of routers they can send packets to. RDP
is intended to be used in place of hosts wiretapping routing protocols (for
example, RIP). It is used instead of, or in addition to, having statically
configured default routes in hosts.
RDP consists of two portions: the server portion runs on routers, and
the client portion runs on hosts. Note that gated treats the portions as
separate protocols, and so only one of them can be enabled at a time.
Each of the portions is described below.
Type man 4 gated.conf at the HP-UX prompt for a description of the
statements used for RDP configuration.
The RDP Server
The RDP server runs on routers, and it is the portion that announces the
routers’ existence to hosts. This is done by periodically multicasting or
broadcasting a Router Advertisement over each physical interface
that has the RDP server enabled on it. Each Router Advertisement
contains a list of all addresses on a physical interface and their
preference for being used as a default router. You can configure the
length of time (the “lifetime”) you want addresses to remain on the list.
At first, Router Advertisements occur every few seconds, and then they
begin occurring every few minutes. You can configure the minimum and
maximum intervals for Router Advertisements to occur. Also, a host can
send a Router Solicitation, requesting an advertisement, and the
router responds with a unicast Router Advertisement unless a multicast
or broadcast advertisement is due to occur.
On hosts that support IP multicasting, Router Advertisements are sent,
by default, to the all-hosts mulicast address 224.0.0.1. If desired, you
can specify in the configuration that broadcasting is to be used for
sending Router Advertisements. This might be needed because a
particular host does not support IP multicasting, or because one or more
hosts on an attached network do not support IP multicasting. If Router
Advertisements are being sent to the all-hosts multicast address, or an
interface is configured for the limited-broadcast address