Question

Given a network topology of 3 or more routers with an OSPF addressing scheme, implement single-area OSPF routing.

Answer 1

The answer for this is as follows:

When configuring any OSPF router, you must establish which area assignment to enable the interface for. OSPF has some basic rules when it comes to area assignment. You can configure OSPF in one area;you can choose any area, although good OSPF design dictates that you configure area 0.

To enable OSPF on cisco routers and advertise interfaces, the following tasks are required.:

Step 1: Use the command router ospf process ID to start OSPF.

Step 2: Use the network command to enable the interfaces.

Step 3: Identify area Assignments.

Step 4: (Optional) Assign the router ID.

Example: Configuring OSPF in a Single Area:

router ospf 1

network 0.0.0.0 255.255.255.255 area 0

Above example displays OSPF with a process ID of 1 and places all interfaces configured with an IP address in area 0. The network command network 0.0.0.0 255.255.255.255 area 0 dictates that you do not care(255.255.255.255) what IP address is, but if an IP address is enabled on any interface, place it in area 0.

The following is a list of reasons OSPF is considered a better routing protocol than RIP:

1)OSPF has no hop count limitations.(RIP has 15 hops only).

2) OSPF understands variable-length subnet mask, and allows for summarization.

3) OSPF uses multicasts(not broadcasts) to send updates.

4)OSPF converges much faster than RIP, because OSPF propogates changes immediately .

5)OSPF allows for tagging of external routes injected by other autonomous system.