IS-IS Packet Types for Routing Updates

B

The correct answer is B. LSP.

IS-IS (Intermediate System-to-Intermediate System) is a link-state routing protocol that is used to exchange routing information between routers within a single autonomous system (AS). Like other link-state protocols, IS-IS builds a complete topology map of the network, which enables routers to calculate the shortest path to any destination.

IS-IS uses a variety of packet types to perform different functions, including:

A. IIH (IS-IS Hello) packets, which are used to establish and maintain adjacencies between routers.

B. LSP (Link State Protocol) packets, which are used to carry routing updates. LSPs contain information about the state of the network, including the router's ID, the list of neighbors, and the status of network links.

C. PSNP (Partial Sequence Number PDU) packets, which are used to request missing LSPs from neighboring routers.

D. CSNP (Complete Sequence Number PDU) packets, which are used to synchronize LSP databases between routers.

In summary, the LSP packet is used to carry routing updates in IS-IS. When a router has new information about the state of the network, it creates an LSP and floods it out to all its neighbors, who in turn forward it to their neighbors, until all routers in the AS have a copy of the updated LSP database.