ospf router id
CCNA
OSPF Hello Packets: Structure, Timers, and Troubleshooting
OSPF Hello packets are Type 1 packets. Routers send them out 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. Nearly every OSPF problem you’ll ever troubleshoot starts here. Routers send Hello packets as multicast, to 224.0.0.5 (AllSPFRouters)....
CCNA
Cisco Router Interfaces: Types, Configuration, and Troubleshooting
Every router interface falls into one of two broad categories: physical, where actual traffic enters and exits over real cabling or radio, and logical, which exist purely in software but serve genuinely important roles — a stable router ID, a VPN endpoint, a way to carve one physical port into many logical ones. Knowing which...