2.4.11 Packet Tracer – Modify Single-Area OSPFv2 Answers

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Answers Note: Red font color or gray highlights indicate text that appears in the instructor copy only.

Addressing Table

Objectives

Part 1: Modify OSPF Default Settings

Part 2: Verify Connectivity

Scenario

In this activity, OSPF is already configured and all end devices currently have full connectivity. You will modify the default OSPF routing configurations by changing the hello and dead timers and adjusting the bandwidth of a link. Then you will verify that full connectivity is restored for all end devices.

Instructions

Part 1:  Modify OSPF Default Settings

Step 1:  Test connectivity between all end devices.

Before modifying the OSPF settings, verify that all PCs can ping the web server and each other.

Step 2:  Adjust the hello and dead timers between R1 and R2.

1. Enter the following commands on R1.

Open configuration window

R1(config)# interface s0/0/0

R1(config-if)# ip ospf hello-interval 15

R1(config-if)# ip ospf dead-interval 60

2. After a short period of time, the OSPF connection with R2 will fail, as shown in the router output.

00:02:40: %OSPF-5-ADJCHG: Process 1, Nbr 209.165.200.225 on Serial0/0/0 from FULL to DOWN, Neighbor Down: Dead timer expired

00:02:40: %OSPF-5-ADJCHG: Process 1, Nbr 209.165.200.225 on Serial0/0/0 from FULL to DOWN, Neighbor Down: Interface down or detached

Both sides of the connection need to have the same timer values in order for the adjacency to be maintained. Identify the interface on R2 that is connected to R1. Adjust the timers on the R2 interface to match the settings on R1.

R2(config)# interface s0/0/0

R2(config-if)# ip ospf hello-interval 15

R2(config-if)# ip ospf dead-interval 60

After a brief period of time you should see a status message that indicates that the OSPF adjacency has been reestablished.

00:21:52: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.10.5 on Serial0/0/0 from LOADING to FULL, Loading Done

Step 3:  Adjust the bandwidth setting on R1.

1. Trace the path between PC1 and the web server located at 64.100.1.2. Notice that the path from PC1 to 64.100.1.2 is routed through R2. OSPF prefers the lower cost path.

C:\> tracert 64.100.1.2

Tracing route to 64.100.1.2 over a maximum of 30 hops:

1 1 ms 0 ms 8 ms 172.16.1.1

2 0 ms 1 ms 0 ms 172.16.3.2

3 1 ms 9 ms 2 ms 209.165.200.226

4 * 1 ms 0 ms 64.100.1.2

Trace complete.

2. On the R1 Serial 0/0/0 interface, set the bandwidth to 64 Kb/s. This does not change the actual port speed, only the metric that the OSPF process on R1 will use to calculate best routes.

R1(config-if)# bandwidth 64

3. Trace the path between PC1 and the web server located at 64.100.1.2. Notice that the path from PC1 to 64.100.1.2 is redirected through R3. OSPF prefers the lower cost path.

C:\> tracert 64.100.1.2

Tracing route to 64.100.1.2 over a maximum of 30 hops:

1 1 ms 0 ms 3 ms 172.16.1.1

2 8 ms 1 ms 1 ms 192.168.10.6

3 2 ms 0 ms 2 ms 172.16.3.2

4 2 ms 3 ms 1 ms 209.165.200.226

5 2 ms 11 ms 11 ms 64.100.1.2

Trace complete.

Close configuration window

Part 2:  Verify Connectivity

Verify that all PCs can ping the web server and each other.

End of document

Answer scripts

Router R1

interface s0/0/0

 ip ospf hello-interval 15

 ip ospf dead-interval 60

 bandwidth 64

Router R2

interface s0/0/0

 ip ospf hello-interval 15

 ip ospf dead-interval 60

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