In order for two OSPF routers to establish neighbor adjacency, which two hello packet values must match?

For two OSPF routers to establish neighbor adjacency, it is essential that the hello interval and dead interval values match between the routers. The hello interval is the time interval at which OSPF routers send hello packets to discover and maintain neighbor relationships. The dead interval represents the period after which a neighbor is considered down if no hello packets are received.

When both of these intervals are consistent between the two OSPF routers, they can successfully communicate and establish an adjacency. This is critical for the routers to exchange routing information and maintain a stable OSPF network.

Matching these intervals ensures that both routers have a common understanding of how often to send and expect hello packets, as well as how long to wait before declaring a neighbor as down. Without this synchronization, OSPF routers will not be able to complete the neighbor establishment process, leading to communication issues in the routing layer.