04-25-2012 11:29 AM - edited 03-04-2019 04:09 PM
Hi All,
I found documentation that OSPF will forego the same "subnet" check for adjacencies on point-to-point links. Is this true?
David
Solved! Go to Solution.
04-25-2012 02:55 PM
Hello David,
I found documentation that OSPF will forego the same "subnet" check for adjacencies on point-to-point links. Is this true?
Not entirely. On point-to-point links, OSPF will ignore the subnet mask mismatch. However, the neighbors still have to be on a common subnet, i.e. from the viewpoint of one router, the second router's IP address must fall within the interface network of the first router.
However, what you read is true for point-to-point unnumbered links. On unnumbered links, it is unavoidable that the two routers are on different subnets. Here, OSPF ignores both the common subnet and the netmask check, and proceeds to create an adjacency if the remaining criteria are met (identical timers, area numbers and types, authentication).
Best regards,
Peter
04-25-2012 02:55 PM
Hello David,
I found documentation that OSPF will forego the same "subnet" check for adjacencies on point-to-point links. Is this true?
Not entirely. On point-to-point links, OSPF will ignore the subnet mask mismatch. However, the neighbors still have to be on a common subnet, i.e. from the viewpoint of one router, the second router's IP address must fall within the interface network of the first router.
However, what you read is true for point-to-point unnumbered links. On unnumbered links, it is unavoidable that the two routers are on different subnets. Here, OSPF ignores both the common subnet and the netmask check, and proceeds to create an adjacency if the remaining criteria are met (identical timers, area numbers and types, authentication).
Best regards,
Peter
04-26-2012 06:36 AM
Peter,
Thanks for the insight. That cleared things up quite a bit!
David
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: