As shown in the figure, OSPF Hello packets are transmitted to multicast address 224.0.0.5 in IPv4 and FF02::5 in IPv6 (all OSPF routers) every:
- 10 seconds (default on multiaccess and point-to-point networks)
- 30 seconds (default on nonbroadcast multiaccess [NBMA] networks; for example, Frame Relay)
The Dead interval is the period that the router waits to receive a Hello packet before declaring the neighbor down. If the Dead interval expires before the routers receive a Hello packet, OSPF removes that neighbor from its LSDB. The router floods the LSDB with information about the down neighbor out all OSPF-enabled interfaces.
Cisco uses a default of 4 times the Hello interval:
- 40 seconds (default on multiaccess and point-to-point networks)
- 120 seconds (default on NBMA networks; for example, Frame Relay)