Neighbor Full Relationship Requirements in OSPF

Question

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

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.