link-state protocol
CCNA
OSPF Passive Interfaces: Configuration and Best Practices
In OSPF (Open Shortest Path First), a passive interface is an interface on which the router stops sending OSPF Hello packets, while still advertising that interface’s connected network in OSPF. Because no Hellos are sent, no OSPF neighbor adjacency can form on that link — but the subnet remains reachable and advertised to the rest...
CCNA
OSPF Encapsulation: How an OSPF Message Is Wrapped for Delivery
Open Shortest Path First (OSPF) operates at the network layer, but it doesn’t travel across a network on its own — every OSPF message gets wrapped in a stack of headers before it ever leaves a router’s interface. Understanding exactly how that wrapping works, layer by layer, is essential for reading a packet capture correctly...