Lesson 2

Static and Dynamic Routing

5-13

the table entries automatically. Static and dynamic routing both provide the same level

of router performance. The drawbacks of static routing are the amount of manual

maintenance the process requires and the routers’ inability to compensate for changes

in the network configuration. Dynamic routing enables routers to compensate for a

failed router or WAN link, but it can generate a considerable amount of additional net-

work traffic.

The decision to use static or dynamic routing depends on your routing strategy for the

entire enterprise, not just the routers connecting remote networks. If you are using

routers to connect multiple LANs at each site, these routers’ tables must have entries

that direct traffic destined for other networks to the WAN routers in addition to their

internal routing entries. The WAN router tables must have entries that enable them to

forward traffic to the appropriate remote site.

Planning

When you consider the number of networks, routers, and sites that make up your

enterprise, you can decide whether the amount of time and effort needed to maintain static

routes is worth the savings in network traffic.

Real World Modifying Routing Tables

The traditional tool for modifying routing tables on a TCP/IP computer, dating

back to the earliest UNIX incarnations, is a command line program called route.

Most operating systems include a version of this tool; in Windows Server 2003

(and all other versions of the Microsoft Windows operating system), the program

is called Route.exe. Using Route.exe’s four subcommands (PRINT, ADD, DELETE,

and CHANGE), you can create new routing table entries and modify or delete

existing ones.

The ROUTE PRINT command displays the contents of the routing table on a com-

puter running a Windows operating system, as in the following example:

Network Destination

Netmask

Gateway

Interface

Metric

0.0.0.0

0.0.0.0

192.168.2.99

192.168.2.2

1

127.0.0.0

255.0.0.0

127.0.0.1

127.0.0.1

1

192.168.87.0

255.255.255.0

192.168.2.21

192.168.2.2

2

192.168.2.0

255.255.255.0

192.168.2.2

192.168.2.2

1

192.168.2.2

255.255.255.255

127.0.0.1

127.0.0.1

1

192.168.2.255

255.255.255.255

192.168.2.2

192.168.2.2

1

224.0.0.0

224.0.0.0

192.168.2.2

192.168.2.2

1

255.255.255.255

255.255.255.255

192.168.2.2

192.168.2.2

1