Network Troubleshooting - Windows Server 2003 Networking Recipes

Information Technology Reference

In-Depth Information

The following command will clear the contents of the routing table on the local computer,

which is useful if a manually created route is incorrect or out of date:

> route -f

If you need to manually create a route to address a connectivity issue, the following

command will specify that traffic to a remote network with the network address of 192.168.2.0

should be sent through the gateway with an IP address of 10.0.0.145 , and will mark the route

as persistent:

> route -p add 192.168.2.0 255.255.255.0 10.0.0.145

■ Note If you use the -f switch before adding or editing a routing table entry, the routing table will be

cleared before the new entry is added or modified.

Likewise, the following command will remove the routing entry associated with the

157.0.0.0 remote network:

> route delete 157.0.0.0

How It Works

In order to transmit traffic to computers located on remote networks, all TCP/IP-enabled

computers will maintain a routing table in memory. This table serves as a kind of “traffic

officer” to determine how the local computer will transmit network packets based on its desti-

nation IP address. A TCP/IP-enabled computer will route all IP packets on the basis of the next-

hop address . If the destination host is on the same network as the source, the next-hop address

will be that of the destination computer. If the destination is on a remote network, the next-hop

address will be a router or gateway on the local network; once the packet reaches the router, it

will determine the subsequent next-hop address, and this process will repeat until the packet

is routed to its ultimate destination.

In most cases, all remote traffic will be routed to a single default gateway; the routing table

will be created and maintained automatically. In more complex routing environments, you

may need to use the route utility to manually create, manage, and delete routing table entries

to specify the path that particular remote traffic should traverse.