2 Replies Latest reply: Jun 14, 2019 6:12 AM by emmanuel RSS

    Can anyone clearly differentiate what the ADV router and Link ID are with ospf lsa type 2,3,4 and 5

    emmanuel

      Hello, I need clarity on the difference between the ADV router and link ID with LSA type 2,3,4 and 5. My current understanding is this:

      when a number of routers are connected to thesame area, they exchange router LSA's. The result of the different LSA's each router has received is then grouped with one LSA header (which is usually the router ID) to be sent to neighbours. In the case of a an LSA Type 1, the link ID from the output from the command "show ip ospf database" is the LSA header that contains the different LSA's the originating router has. The ADV ID is the router-ID of the router that sent the LSA. in the case of a type 1 LSA, Which is a router LSA, both the Link ID and the ADV ID would be thesame however in the case of a type 2 LSA. They would be different becasuse the router that originated the LSA would be different from the Designated router that is saddled with the responsibility of forwarding LSA's to other routers in the area. But i just read this article:

      https://community.cisco.com/t5/networking-documents/reading-and-understanding-the-ospf-database/ta-p/3145995

      And the knowledge I have of both the ADV router and the Link regarding type 2 lsa's don't add up. I'll really appreciate if this is cleared up with a network diagram to aid understanding. Many thanks