Monitoring and Troubleshooting Multi-area
isco's IOS has several debug and show commands that can be useful
in monitoring and troubleshooting OSPF networks. Following is a sampling
of these commands, which can be used to gain information about various
debug ip ospf events
Shows information concerning OSPF events,
such as the selection of a designated router and the formation of router
debug ip ospf packet
Shows information contained in each OSPF
packet, such as Router ID and Area ID.
show ip ospf border-routers
Shows an ABR's internal routing
show ip ospf virtual-links
Shows the status of a router's
show ip ospf neighbor
Shows neighbor router information, such as
Neighbor ID and the state of adjacency with the neighboring router.
show ip ospf process-id
Shows area information, such as identify-
ing the area's area border router or autonomous system boundary router.
show ip ospf database
Shows information about a router's OSPF
database, such as a router's router link states and network link states.
n this chapter, we illustrated the scalability constraints of an OSPF net-
work with a single area. We introduced the concept of multi-area OSPF as a
solution to these scalability limitations.
We identified the different categories of routers used in multi-area config-
urations. These router categories include backbone router, internal router,
area border router, and autonomous system boundary router. We explored
how these routers can use summarization and default routes to reduce the
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