Deploying a Large-Scale IS-IS Network
Question
You are asked to deploy a large-scale IS-IS network with multiple areas.
Which two statements are true? (Choose two.)
Answers
Explanations
Click on the arrows to vote for the correct answer
A. B. C. D.BD
IS-IS (Intermediate System to Intermediate System) is a link-state routing protocol used in large-scale networks such as Service Provider networks. In IS-IS, the network topology is divided into areas, which are collections of routers that share the same database of link-state information. The backbone area is the central area that connects all other areas in the network.
In a large-scale IS-IS network, it is common to have multiple areas to scale the network and to reduce the size of the link-state database. When deploying such a network, the following statements are true:
B. Level 2 routers can route between areas: In IS-IS, there are two types of areas: Level 1 (L1) and Level 2 (L2). Level 1 areas are connected to the backbone area and can only route within their own area. Level 2 areas are connected to the backbone area and can route between other Level 2 areas, but they cannot route to Level 1 areas. Level 2 routers are used to connect different Level 1 areas together, and they are responsible for forwarding traffic between Level 1 areas. Therefore, statement B is true.
D. A collection of Level 2 routers in different areas constitute the backbone in the network: The backbone area is the central area that connects all other areas in the network. In IS-IS, the backbone area is made up of Level 2 routers. Therefore, a collection of Level 2 routers in different areas constitutes the backbone of the network. This backbone is responsible for routing traffic between different Level 2 areas. Therefore, statement D is true.
A. A collection of Level 1 routers in different areas constitute the backbone in the network: This statement is not true. Level 1 routers cannot route between different areas, and they do not belong to the backbone area. The backbone area is made up of Level 2 routers.
C. Level 1 routers can route between areas: This statement is also not true. Level 1 routers can only route within their own area and cannot route to other areas. They rely on Level 2 routers to forward traffic between different areas.
In summary, when deploying a large-scale IS-IS network with multiple areas, Level 2 routers are used to route between areas, and a collection of Level 2 routers in different areas constitutes the backbone of the network.
