Hi Radha, The forwarding address (next-hop) for an AS-External LSA may be advertised if it is reachable via an OSPF inter-area or intra-area route. You included connected routes in your question and this is not necessarily correct since a connected route will only be accessible to other OSPF routers in the domain if it is advertised in OSPF. For NSSA LSAs, the next-hop should be reachable via an intra-area route in the NSSA.
Some implementations limit the advertising to the case where the next-hop is on a multi-access network. Hope this helps, Acee From: OSPF <[email protected]<mailto:[email protected]>> on behalf of Radha Danda <[email protected]<mailto:[email protected]>> Date: Wednesday, July 13, 2016 at 7:15 AM To: OSPF WG List <[email protected]<mailto:[email protected]>> Subject: [OSPF] FW: Forwarding address set for type-5 Hi All, I need clarification on setting the Forwarding address set for type-5 LSA. As per RFC 2328 it is not obviously mentioned anywhere that the forwarding address can be set to connected, inter-area or intra-area routers but in the section 16.4 (Calculating AS external routes) it is mentioned that the forwarding address can be set to inter-area or intra-area as well. Snippet from the RFC is provided below for quick reference. Can you please confirm if the forwarding address can be set to ospf connected, inter-area or intra-area route while generating external LSA. Thanks. ********************************** If the forwarding address is non-zero, look up the forwarding address in the routing table.[24] The matching routing table entry must specify an intra-area or inter-area path; if no such path exists, do nothing with the LSA and consider the next in the list. ****************************** Best Regards, Radha
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