OSPF Hello Packets: Structure, Timers, and Troubleshooting
OSPF Hello packets are Type 1 packets. Routers send them on every OSPF-enabled interface, including virtual links. Their job is simple: find neighbors, and keep those neighbor relationships alive. It’s a small packet with a big job, and nearly every OSPF problem you’ll ever troubleshoot starts here. Routers send Hello packets as multicast, to 224.0.0.5...
