I have a few questions about the OSPF topology attached. Please comment/suggest on questions in seperate comments so that I can rate them individually.
1) Dont see R5, R2 and R4 in attached topology diagram, this is about R1 and R3. R1's loopback interface has an ip of 172.16.8.193/27. I did not issue bandwidth command in interfaces (for testing purposes), so all serial and frame-relay connections between R1 and R3 has a cost of 64.
Under these circumstances, R3 does not do equal cost load sharing. Only 1 entry for 172.16.8.193/29 appears in route table, which is via frame-relay. But if I establish a virtual-link and Area 1 becomes transit area, equal cost balancing occurs. But in fact, I have a valid OSPF relation over Point-To-Point link as described behaviour in below question. Can you please explain this and normal behaviour in this scenario?
2) Dont see R5, R2 and R4 in attached topology diagram, this is about R1 and R3. R3's loopback interface has an ip of 172.16.8.193/29. I did not issue bandwidth command in interfaces (for testing purposes), so all serial and frame-relay connections between R1 and R3 has a cost of 64. There is no virtual link configured
Under these circumstances, R3 has an interface in Area 0 to operate in OSPF correctly. For testing purposes, I removed the loopback 172.16.8.193/27, from R1 in posted diagram and added it to R3 (So L0/0 of R3 belongs to area 0 temporarily, unlike the diagram). Then I started pinging loopback interface of R3 from R1. Then I disabled ser1/0 interface of R3, which is the frame-relay interface that connects R3 to backbone area. Ping was not successfull, untill the dead time expired. After a lot of lost pings and reached dead time, pings came back, pings are successfull. How? R3 neither has an interface in Area 0 nor Area 1 is a transit area! When I issue âsh ip ospfâ in R3, I see âArea BACKBONE(0) (Inactive)â. And in route table of R3, I see 172.16.8.193/27 marked as IA (Inter Area)? Is it treating Area 1 as Backbone area when its interface in Area 0 is failed? Can you please explain this and normal behaviour in this scenario?
3) Dont see R5, R2 and R1 in attached topology diagram, this is about R3 and R4. F0/0 of R3 has an ip of 172.16.10.1/25, and L0 of R3 has an ip of 172.16.10.129/25. R4's loopback interfaces, which belongs to Area 3 are 172.16.11.1/25 and 172.16.11.129/25
Under these circumstances, I apply âarea 2 range 172.16.10.0 255.255.255.0â command in R3, then R1 gets the summarized one single route, thats fine. As you can see, R4 does not have an interface in Area 0, and we have to configure a virtual-link for area 3 connectivity. When I apply virtaul link and Area 2 becomes transit area, R1 gets Area 3 routes fine, but Area 2 routes, which is now a transit area, are all displayed without being summarized. Both summarized and not-summarized routes of Area 2 appear in route table of R1. Can you please explain this and normal behaviour in this scenario?
Any comments appreciated!