OSPF hello interval and dead interval

OSPF hello interval and dead interval are configurable time parameters that

  • maintain connectivity between OSPF neighbors through regular hello packet exchanges,

  • detect neighbor failures when hello packets are not received within the specified timeframes, and

  • must be consistent across all routers within the same network to ensure proper operation.

Hello interval and dead interval configuration details

OSPF hello packets are packets that an OSPF process sends to its OSPF neighbors to maintain connectivity with those neighbors. The hello packets are sent at a configurable interval (in seconds). The defaults are 10 seconds for an Ethernet link and 30 seconds for a non broadcast link.

Hello packets include a list of all neighbors for which a hello packet has been received within the dead interval. The dead interval is also a configurable interval (in seconds), and defaults to four times the value of the hello interval. The value of all hello intervals must be the same within a network. Likewise, the value of all dead intervals must be the same within a network.

These two intervals work together to maintain connectivity by indicating that the link is operational. If a router does not receive a hello packet from a neighbor within the dead interval, it will declare that neighbor to be down.