Step 1: Connect the equipment

Using a crossover serial cable, connect the serial interface of each router to the other routers, as shown in the topology diagram. Note the DTE vs. DCE end of the connection.

Step 2: Perform basic configuration on the routers

  1. Connect a PC to the console port of the routers to perform configurations using a terminal emulation program.
  2. Configure Routers 1, 2, and 3 with a hostname, console, Telnet, and privileged passwords according to the table and topology diagram.

Step 3: Configure single area OSPF routing on the routers

Configure basic OSPF routing on the routers. All networks are in Area 0.

Step 4: Verify current OSPF operation

Now that the serial interfaces and OSPF have been configured, OSPF should be operational between the routers.

  1. Use the show ip route command on all the routers to verify operation. The outputs should be similar to what is shown below. All networks should be listed in the routing table of each router
  2. Use the show interfaces serial 0/0/0 command to determine the bandwidth settings on the serial interfaces.

Step 5: Configure serial interface bandwidth settings

The metric used by OSPF is cost. On Cisco routers, cost is derived from the bandwidth setting on the interfaces.

  1. Configure the bandwidth on the serial 0/0 interface of R1.
  2. Use the show interfaces serial 0/0/0 command on R1.
  3. Again use the show ip route command on R1.

Step 6: Use ospf cost to determine route selection

Another method that is used to determine the path chosen by OSPF is to dictate the cost of an interface.

How is this cost calculated? Jawaban:  There is a T1 (1.544 Mbps) speed link from R1 to R3 and a 64 Kbps link from R3 to get to the 10.0.0.0/30 network. The cost of the T1 link is 64 (100,000,000 / 1,544,000) and the cost of the 64 Kbps link is 1562 (100,000,000 / 64,000). 64 + 1562 = 1626 total cost of route from R1 to 10.0.0.0. The router to the 10.0.0.0 network via R3 is now 2000 + 64 = 2064.

Step 7: Reflection

  1. What determines the path chosen by OSPF? Jawaban: Lowest cost.
  2. What has a more direct effect on the OSPF cost of a link: the bandwidth setting or the ip ospf cost setting? Jawaban: The ip ospf cost setting.