How Routing Protocols Work; Router - HP ProCurve Secure Router 7203 dl Advanced Management And Configuration Manual

Dynamic Routing Protocols Supported on the ProCurve Secure

Router

The ProCurve Secure Router supports three routing protocols—each of which
it can use alone or in conjunction with the others:
Routing Information Protocol (RIP) versions 1 and 2
Open Shortest Path First (OSPF) version 2
Border Gateway Protocol (BGP) version 4
RIP and OSPF are Interior Gateway Protocols (IGPs); they are designed to
operate in a single autonomous system (AS). (An AS is a group of networks
administered by the same authority). Although they are IGPs, RIP v2 can be
used to learn external routes, and OSPF allows a router to redistribute or
advertise external routes to other routers in the OSPF network.
BGP is an Exterior Gateway Protocol (EGP), which allows routers in different
autonomous systems to exchange routes. Because BGP routers must regulate
traffic between networks controlled by organizations with different policies—
and at times competing aims—BGP is designed to allow administrators to
customize a policy for route exchange. On the ProCurve Secure Router, BGP
provides IP services for private networks.

How Routing Protocols Work

A router constructs its routing table using the information it receives from
other routers. The router changes its routing table in response to routing
updates that provide additional information or notification that conditions in
the network have changed (for example, a link has failed). This responsive-
ness explains why using a routing protocol is often called dynamic routing.
A routing protocol governs how routers exchange routes and other network
information with each other. The protocol must dictate parameters such as
the following:
How routers compute a route's metric and select the best route for their
routing table—Routing protocols can have a relatively complicated sys-
tem for calculating a route's metric. Usually, you do not need to under-
stand exactly how this calculation is performed. However, you should
understand the criteria that the routing protocol uses to calculate a route,
so that you can select the best routing protocol (or protocols) for your
network environment. If necessary, you can change which routes are
chosen by altering the default metrics that a protocol assigns certain
routes.
IP Routing—Configuring RIP, OSPF, BGP, and PBR
Overview
13-7