Building a Small Network with Static Routing

By Edward Tetz

To illustrate static routing the example will be a small network with two routers and two workstations, with the workstations placed on the far ends of the network. On it, the routers are configured so that the FastEthernet 0/0 (fa0/0) interfaces are for the computer side of the network and the FastEthernet 0/1 (fa0/1) interfaces are for the external side.


Initially, if you sit at Computer1 and attempt to contact Computer2, you cannot make the connection. If you use commands such as ping or traceroute (tracert on Windows) on Computer2 to troubleshoot the connection, you receive the following results:

Pinging with 32 bytes of data:
Reply from Destination host unreachable.
Reply from Destination host unreachable.
Reply from Destination host unreachable.
Reply from Destination host unreachable.

If your network has only one router, what routing do you need to deal with? Other than enabling routing on the router, nothing needs to be done, because the router automatically adds routes in its routing table for all directly connected interfaces. So if you take a look at the interfaces on the router, you find a list of interfaces like the following:

Router2#show ip interface brief
Interface               IP-Address      OK? Method Status       Protocol
FastEthernet0/0   YES NVRAM  up                 up
FastEthernet0/1     YES manual up                 up
Loopback0      YES manual up                 up

Now, if you look at the routing table (using the show ip route command) and specify that it show the connected interfaces, you see two routes that allow data to be transferred between these two interfaces. When data arrives on one interface, if it is destined for the other network segment, it is passed through the other interface.

Router1#show ip route connected
C is directly connected, FastEthernet0/1
C is directly connected, FastEthernet0/0

In addition to the routing table, you can also get data about your routes from the show ip route summary command, which shows a list of networks or subnets for your connected interfaces.

Router1#show ip route summary
IP routing table name is Default-IP-Routing-Table(0)
IP routing table maximum-paths is 16
Route Source    Networks    Subnets     Overhead    Memory (bytes)
connected       2           0           144         272
static          0           0           0           0
Total           2           0           144         272