I have a question about originating a type 4 summary LSA when a router has an intra-area route (via area A) to an ASBR as well as a lower cost inter-area route (via the backbone) to the same ASBR through another ABR.
According to the sixth bullet in section 12.4.3 of RFC 2328: Else, if the destination of this route is an AS boundary router, a summary-LSA should be originated if and only if the routing table entry describes the preferred path to the AS boundary router (see Step 3 of Section 16.4). If so, a Type 4 summary-LSA is originated for the destination, with Link State ID equal to the AS boundary router's Router ID and metric equal to the routing table entry's cost. Note: these LSAs should not be generated if Area A has been configured as a stub area. According to section 16.4 item (3), the preferred route to the ASBR would be the least cost route i.e. the inter-area route, since RFC1583Compatibility is enabled. Thus, as far as I can tell, we would generate a type 4 summary when processing the inter-area route entry and advertise the summary into area A and not generate the corresponding summary into the backbone. This would be different than RFC 1583 behavior or RFC 2328 behavior with RFC1583Compatibility disabled. In those two cases, we would generate a type 4 summary into the backbone and areas other than A when processing the intra-area route entry, since the intra-area route would be the preferred route. Is this the correct interpretation of sections 12.4.3 and 16.4? Thanks in advance for any responses. -Nischal _______________________________________________ OSPF mailing list [email protected] https://www.ietf.org/mailman/listinfo/ospf
