So a buddy of mine and I are disputing the actual layer OSPF runs at. He states OSPF is purely layer 3. I say OSPF is layer 4. Since IP is required for OSPF to work, the OSPF is encapsulated in IP. To me, if you encapsulate anything in a L3 protocol (IP) then in all reality it is L4 at that point -- and OSPF, as a protocol, implements it's own messaging rules as TCP or UDP would. So I consider that a transport protocol since OSPF is not using TCP or UDP. There is so much conflicting information out there that this is a total grey area! Anybody want to chime in? :) Thanks!
I have this problem too.