Could some one explain to me what "The same autonomous system" means with regards to the neighbor full relationship requirement rules in OSPF. Does it need to be the same across all areas of my OSPF routed network?

  1. Same Autonomous System
  2. Same Subnet Mask
  3. Same Hello and Dead
  4. Same Authentication

1 Answer 1


From the OSPF perspective, an autonomous system is the collection of OSPF areas that connect to a single Area 0.

To connect as full neighbors on a link, the prospective neighbors need to be in the same OSPF area, have a common subnet with the same mask, the same timers, and the same authentication.

  • 1
    MTU can also be a factor. Sep 28, 2015 at 17:47
  • Yes, sorry, I answered this prior to consuming the necessary amount of caffeine this morning..
    – Ron Maupin
    Sep 28, 2015 at 21:51
  • Hah, I think we're all guilty of that. Just wanted to make sure it was included. Sep 28, 2015 at 21:59
  • @RonMaupin obligatory CommitStrip
    – JFL
    Aug 27, 2017 at 18:14

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