TMS zl Management and Configuration Guide ST.1.0.090213

9-9
Routing
Dynamic Routing
Dynamic Routing
As a network becomes larger and more complicated, manually configuring
every route on every router becomes infeasible. Even when you use default
routes and hub routers to minimize the number of routes individual routers
must know, manually configuring routes for an expanding a network can be
time consuming.
Instead of configuring static routes, you can use dynamic routing protocols,
which enable routers to exchange routing information with other routers in
the network. Each router can then use this information to build its routing
table.
The TMS zl Module supports two dynamic routing protocols: RIP versions 1
and 2 and OSPF version 2. RIP and OSPF are Interior Gateway Protocols
(IGPs) and 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.
How Routing Protocols Work
The module constructs its routing table using the information it receives from
other modules and routers. The module 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
responsiveness 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,