Lab 9.3.4 Troubleshooting OSPF Default Route Redistribution

Step 1: Connect the equipment

1. Cable the network as shown in the topology diagram.
2. Connect Host 1 to the console port of Router 1 using a console cable to perform configurations.

Step 2: Perform basic configuration on Router 1

Configure Router 1 with a hostname, assign IP addresses to interfaces, assign privileged passwords, and configure for secure console and Telnet access according to the addressing table and topology diagram. Configure OSPF to advertise networks between routers. Save the configuration. This router will serve as an internal router to the network.

Step 3: Perform basic configuration on Router 2

Perform basic configuration on Router 2 with a hostname, assign IP addresses to interfaces, assign privileged passwords, and configure for secure console and Telnet access according to the addressing table and topology diagram. Configure OSPF to advertise networks between routers 1 and 2. Save the configuration. This router will serve as the router connecting the network to the ISP.

Step 4: Perform basic configuration on Router 3

Perform basic configuration on Router 3 with a hostname, assign IP addresses to interfaces, assign privileged passwords, and configure for secure console and Telnet access according to the addressing table and topology diagram. OSPF will not be configured on this router. Save the configuration. This router will serve as the ISP side router.

Step 5: Configure the hosts with IP address, subnet mask, and default gateway

a. Configure Host 1 and Host 2 with the proper IP address, subnet mask, and default gateway.

1) Host 1 should be assigned 192.168.1.5 /24 and the default gateway of 192.168.1.1.

2) Host 2 should be assigned 10.0.1.10 /24 and the default gateway of 10.0.1.1.

b. Each host should be able to ping its default gateway. If the ping is not successful, troubleshoot as

necessary. Check and verify that the workstation has been assigned a specific IP address and default

gateway.

Step 6: Configure default routing

In this scenario, the devices will have the following functions:

• Router 1 (R1) will be an internal enterprise network router.
• Router 2 (GW) is to serve as the gateway router connecting the network to the ISP.
• Router 3 (ISP) represents the ISP side of the Internet connection.
• Host 1 represents an internal network host.
• Host 2 (or loopback interface) connected to Router 3 represents a resource on the Internet.

Step 7: Troubleshooting default routing

Default routing is susceptible to many of the same issues that can cause problems with any OSPF route propagation

1. Shut down the S0/0/1 interface on Router ISP and observe the routing table on Router R1.
2. Observe that the default route is no longer present.
3. Troubleshooting becomes more difficult when the GW router is configured to always send the default routing information. Configure this option on the GW router now.

Step 8: Reflection

1. Can a default route be advertised by an OSPF router that does not have the next hop in its routing table? Jawaban : Yes, if the default-information originate always command is configured; otherwise, no.
2. List three things that can cause OSPF default route propagation to fail? Jawaban :any OSPF router configuration error or network issue such as: mismatched areas, mismatched timers, incorrect IP addresses, interfaces down, incorrect networks being advertised, etc.
3. What type of OSPF router does a router that injects a default route into the OSPF process become? Jawaban : An Autonomous System Boundary Router, because the default route points to a network outside of the OSPF domain.

What is an advantage and a disadvantage of using the default-information originatecommand over configuring default routes on all routers? Jawaban : An advantage is that it is much easier to configure and manage a single static route and redistribution command than to have to configure on each device. Disadvantages are that any OSPF error can cause the loss of the default route and it tends to be more difficult to troubleshoot