Dynamic routing

OSPF network type

Also called point-to-point, broadcast network, ip ospf network, POINTOPOINT, network type mismatch

How OSPF treats a link: broadcast with a DR election, or point-to-point between two routers with none.

Ethernet defaults to broadcast: a DR and BDR, and a network LSA for the segment. On a link that only ever has two routers, point-to-point skips the election and its wait, and the neighbour shows as Full/-. Both ends must match: with one end broadcast and the other point-to-point the routers still become Full, but describe the link in ways SPF cannot join, and routes through it vanish.

See it on real machines

Learn it on real machines.