IP R
OUTING
3-285Configuring the Open Shortest Path First Protocol
Open Shortest Path First (OSPF) is more suited for large area networks
which experience frequent changes in the links. It also handles subnets
much better than RIP. OSPF protocol actively tests the status of each link
to its neighbors to generate a shortest path tree, and builds a ro uting table
based on this information. OSPF then utilizes IP multicast to propagate
routing information. A separate routing area scheme is also used to further
reduce the amount of routing traffic.
Note: The OSPF protocol implemented in this device is based on
Version 2 (RFC 2328). It also supports Version 1 (RFC 1583)
compatibility mode to ensure that the same method is used to
calculate summary route costs throughout the network when older
OSPF routers exist; as well as the not-so-stubby area option (RFC
1587).
backbone
normal
area
NSSA
isolated
area
stub
AutonomousSystem A
AutonomousSystem B
externalnetwork
Router
ABR
ABR
ABR
ABR
ASBR
ASBR
ASBR
virtual
link