Contents
- 1 How OSPF calculate the best route?
- 2 What is the correct method to configure route summarization on an OSPF router?
- 3 How add route in OSPF?
- 4 What are the two reasons why route summarization is important OSPF?
- 5 How does OSPF propagates external routes into multiple areas?
- 6 How to show OSPF database summary in IP OSPF?
- 7 How does OSPF know if a router is reachable?
How OSPF calculate the best route?
If there are multiple routes to a network with the same route type, the OSPF metric calculated as cost based on the bandwidth is used for selecting the best route. The route with the lowest value for cost is chosen as the best route.
What is the correct method to configure route summarization on an OSPF router?
What is the correct method to configure route summarization on an OSPF router? Configure OSPF and instruct the ABR to summarize specific area routes.
What is area in OSPF routing?
An OSPF network can be divided into sub-domains called areas. An area is a logical collection of OSPF networks, routers, and links that have the same area identification. The router does not have detailed information about network topology outside of its area, which thereby reduces the size of its database.
How add route in OSPF?
Configuring OSPF in a Single Area
- Use the command router ospf process ID to start OSPF.
- Use the network command to enable the interfaces.
- Identify area assignments.
- (Optional) Assign the router ID. Example 3-1 displays OSPF with a process ID of 1 and places all interfaces configured with an IP address in area 0.
What are the two reasons why route summarization is important OSPF?
A key feature of the OSPF protocol is the ability to summarize routes at area and autonomous system boundaries. Route summarization is important because it reduces the amount of the OSPF LSA flooding and the sizes of LSDBs and routing tables, which also reduces the memory and the CPU utilization on the routers.
Where you can manually summarize OSPF?
Route summarization helps reduce OSPF traffic and route computation. OSPF, unlike EIGRP, doesn’t support automatic summarization. Also, unlike EIGRP, where you can summarize routes on every router in an EIGRP network, OSFP can summarize routes only on ABRs and ASBRs.
How does OSPF propagates external routes into multiple areas?
The ABR (Router 2.2.2.2) has installed an external route learned from the ASBR (Router 1.1.1.1) and flooded the external LSA from area 1 into area 0. (External LSAs are flooded unaltered into all areas.) However, the ASBR is not in area 0. Routers in area 0 do not know how to reach the ASBR.
How to show OSPF database summary in IP OSPF?
They are flooded only within the area in which they originate. show ip ospf database summary —Displays the area border router (ABR) summary links. Since Router 2.2.2.2 is the ABR, it has the database for both areas that it is connected to.
Do you need OSPF for inter-area routing?
This document looks into the Open Shortest Path First (OSPF) Database and the Routing table when OSPF runs across two areas. There are no specific requirements for this document. This document is not restricted to specific software and hardware versions.
How does OSPF know if a router is reachable?
If both routers see each other as neighbors, then they are considered reachable. Each router also checks its local neighbor table (which you can see using the show ip ospf neighbor command) to verify that its and the neighbor’s interfaces are on a common IP subnet.