352-001 Question #237: Real Exam Question with Answer & Explanation

The correct answer is A: one LSP: containing the router information, internal routes, and external routes. In IS-IS, each router originates a single LSP (Link State PDU) that contains all of its information: adjacency/link data, internal (intra-area) routes, and external (redistributed) routes. This is fundamentally different from OSPF, which uses separate LSA types (Type 1, 5, 7, etc

Question

An IS-IS router is connected to four links and redistributing 75 routes from RIP. How many LSPs will this router originate?

Options

Aone LSP: containing the router information, internal routes, and external routes
Btwo LSPs: one containing router information and internal routes and one containing external routes
Cthree LSPs: one containing all links, one containing router information, and one containing external
Dsix LSPs: one for each link, one containing router information, and one containing external routing

Explanation

In IS-IS, each router originates a single LSP (Link State PDU) that contains all of its information: adjacency/link data, internal (intra-area) routes, and external (redistributed) routes. This is fundamentally different from OSPF, which uses separate LSA types (Type 1, 5, 7, etc.) for different categories of routing information. Regardless of the number of links (4) or the number of redistributed routes (75 from RIP), IS-IS consolidates everything into one LSP per router (with fragments numbered sequentially if the LSP exceeds MTU, but still considered a single logical LSP from that router). The other options incorrectly apply OSPF-like separation of routing information to IS-IS.

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