Although this module will describe many common problems and solutions for
troubleshooting various routing protocols, it is important to note that there
is no single template for solving Layer 3 problems. Routing problems are solved
with a methodical process, using a series of commands to isolate and diagnose
the problem.
Many of the examples in this module are just that, examples. It is important
to be able to apply these examples and concepts to other routing protocols and
other scenarios.
Here are some areas to explore when diagnosing a
possible problem involving routing protocols:
General Network
Issues Many times a change in the topology, such as a down link, may
have other affects on other areas of the network which might not be obvious at
the time. This may include the installation of new routes, static or dynamic,
removal of other routes, and so on.
Some of the things to consider
include:
Has anything in the network changed recently?
Is there anyone currently working on the network infrastructure?
Connectivity Issues Check for any equipment and connectivity
problems including:
Power problems: outages, intermittent problems, environmental problems such
as overheating, and so on.
Layer 1 problems: cabling problems, bad ports, service provider problems,
and so on.
Some commands, which can be used to check these and other issues,
include:
ping
traceroute
show interfaces, show ip
interface
Neighbor Issues If the routing protocol establishes an
adjacency with a neighbor, check to see if there are any problems with the
routers forming neighbor relationships.
Topology Database If
the routing protocol uses a topology table or database, check the table for
anything unexpected, such as missing entries or unexpected entries.
Routing Table Check the routing table for anything unexpected,
such as, missing routes or unexpected routes. Use debug
commands to view routing updates and routing table maintenance.
Many
troubleshooting issues and solutions are common amongst different routing
protocols. In this module, some issues described on one routing protocol may
also apply to others.