What is contained in an IS-IS CSNP message?
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A. B. C. D.A
In the Intermediate System to Intermediate System (IS-IS) protocol, the CSNP (Complete Sequence Number PDU) message is used to ensure that all routers in an area have the same information about the contents of their respective link-state databases. This message is sent periodically by the designated router (DR) and contains a list of all the Link State Packets (LSPs) that the DR has in its database.
The correct answer to the question is D. The CSNP message contains all of the LSPs in a router's link-state database. Each LSP describes the state of a particular router or network segment in the area, and includes information such as the router or network segment's identity, its neighbors, and the metrics associated with its connections.
Option A (all of the headers of the LSPs in a router's link-state database) is incorrect because the CSNP message doesn't just contain the headers of the LSPs, but the entire LSPs themselves.
Option B (all of the IP routes in a router's link-state database) and option C (all of the IP routes in a router's routing table) are incorrect because the CSNP message only contains information about the LSPs, not the IP routes themselves.
In summary, the CSNP message in IS-IS contains all of the LSPs in a router's link-state database, which provides a complete view of the state of the network.