Chapter 19
| Unicast Routing
Configuring the Open Shortest Path First Protocol (Version 2)
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Figure 481: Resetting RIP Statistics
Configuring the Open Shortest Path First Protocol (Version 2)
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 routing 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 RFC 2328 (Version
2). It also supports RFC 1583 (early Version 2) 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 3101).
Figure 482: Configuring OSPF
Command Usage
â—† OSPF looks at more than just the simple hop count. When adding the shortest
path to any node into the tree, the optimal path is chosen on the basis of delay,
backbone
normal
area
NSSA
isolated
area
stub
Autonomous System A
Autonomous System B
external network
Router
ABR
ABR
ABR
ABR
ASBR
ASBR
ASBR
virtual
link
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