OSPF Cost to ABR

[yuchenglai]

Hi, I was wondering if someone could assist me in regards to calculating cost in OSPF.

Is there a way to determine what routers in an OSPF area is an ABR just by looking into the OSPF Database and then subsequently determining the cost to the ABR from a router that is, for example, 10 hops away from the ABR?

[Jerry Ye · Accepted solution]

If you look at the output of show ip ospf database, LSA type 3 - Summary Net Link States is advertised by ABR.

Example output:

                Summary Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
10.12.11.0      10.255.255.1    1322        0x800001E7 0x0030EE
10.12.11.0      10.255.255.2    113         0x800001E9 0x008A87

To determine the cost (not hop, OSPF doesn't use hop count), if you are using the loopback as the router-id and advertized by your ospf routers, show ip route x.x.x.x should tell you the cost to the ABR.

HTH,

jerry

[yuchenglai]

Jerry, thank you very much; you just made that crystal clear for me!