264
Chapter 5
IP Routing
C 172.16.50.0 is directly connected, Ethernet0
C 172.16.40.0 is directly connected, Serial0
2501C#
Router 2501C can communicate with 2501B since they are on the same
WAN network. However, by default, 2501C cannot see any other router or
remote network.
Configuring IP Routing in Our Network
T
he network in the previous section has now been configured correctly
with IP addressing. However, how does a router send packets to remote net-
works? The routers can only send packets by looking at the routing table and
discovering how to get to the remote networks. But our configured routers
only have information containing directly connected networks in each rout-
ing table. What happens when a router receives a packet with a network that
is not listed in the routing table? It doesn't send a broadcast looking for the
remote network--the router just discards it. Period.
There are a few different ways to configure the routing tables to include
all the networks in our little internetwork so that packets will be forwarded.
However, the best way for one network is not necessarily best for another.
If you understand the different routing types, you'll be able to decide what
fits best in your business requirements.
The different types of routing you will learn about in this chapter are:
Static routing
Default routing
Dynamic routing
We will start off by describing and implementing static routing on our
network. Why? Because if you can implement static routing and make it
work, it means you have a good understanding of the internetwork.
Static Routing
Static routing occurs when an administrator manually adds routes in each
router's routing table. There are both benefits and disadvantages to static
routing, as there are for all routing processes.
Copyright ©2002 SYBEX, Inc., Alameda, CA
www.sybex.com