OSPF

Encapsulation	Message Format

OSPF Types: Hello = 1; DD = 2; LS Request = 3; LS Update = 4; LS Ack = 5.
OSPF is inheritly classless, no summarization at classful boundary.
Loopback interfaces are not advertised in OSPF.
Loopback interface is preferred to use for router-id.
router-id must be distinct.

Router(config)#router ospf 1
Router(config-router)#network 192.168.1.9 0.0.0.3 area 0
Router(config-router)#router-id ip_address
--> otherwise, the highest active IP interface will be picked. Or the first OSPF network command.
Router(config-router)#auto-cost reference-bandwidth 100 (in Mbps)
Router#clear ip ospf process
Router#show ip ospf [interface]
Router#show ip ospf neighbor
Router(config-if)#bandwidth 64 (in Kbps) is equivelant to:
Router(config-if)#ip ospf cost 1562
Router(config-if)#ip ospf priority {0 - 255}
Router(config-if)#ip ospf hello-interval 5 (default is 10, in seconds)
Router(config-if)#ip ospf dead-interval 20 (default is 40, in seconds)
--> intervals must be identical between neighbors.