OSPF Flashcards
LSA
Link State Advertisement - contains info about network topology. Sent to all neighbors in database exchanges
passive interface
an interface that does not participate in the protocol
HELLO
Messages that contain RID, network and timing info. sent to multicast 224.0.0.5
DR
Designated router that ensures other routers in the same subnet remain updated. The router with the highest RID is the DR.
RID
Router ID. A 32-bit identifier. Either the highest loopback address or highest IP address of the interfaces
Basic OSPF configuration
router ospf
network area
Neighbors
A relationship between two routers that share the same link
OSPF metric
sum of the interface costs for all outgoing interfaces in the route
Key troubleshooting commands
show ip protocols
show run
show ip route
OSPF neighbor requirements
areas must match
hello/dead timers must match
interfaces must be up/up
MTU mismatch may cause problems
View neighbors
show ip ospf neighbor
hello timer
The interval a router expects to receive a Hello
dead timer
The max interval a router will wait to receive a Hello (4x times as long as the hello timer)