TMS zl Management and Configuration Guide ST.1.1.100430

9-10
Routing
Dynamic Routing
Note The TMS zl Module can know multiple default routes. The default route with
the lowest administrative distance (or, in the case of a tie, the lowest admin-
istrative distance and the lowest metric) takes precedence.
For example, the module might learn a default route from a routing protocol,
and you might create a static default route as well. The route with the lower
administrative distance is used.
You can also create multiple static default routes. For example, you could
create one default route over a primary GRE tunnel and another default route
over a secondary GRE tunnel. The route with the lower administrative dis-
tance and metric is used unless the associated tunnel interface goes down, in
which case, that route is removed from the routing table and the second
default route is added.
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.