Troubleshooting Switches
There are many ways to troubleshoot a switch. Developing a troubleshooting approach or
test plan works much better than using a hit-or-miss approach. Here are some general
suggestions to make troubleshooting more effective:
?– Take the time to become familiar with normal switch operation: The Cisco website
(Cisco.com) has a lot of technical information that describes how its switches work.
The con?¬?guration guides in particular are helpful.
?– For more large multiswitch environments, have an accurate physical and logical
map of the network on hand: A physical map shows how the devices and cables are
connected. A logical map shows what segments (VLANs) exist in the network and
which routers provide routing services to these segments. A spanning-tree map is also
useful for troubleshooting complex issues. Because a switch can create different
segments by implementing VLANs, the physical connections alone do not tell the
whole story. You must know how the switches are con?¬?gured to determine which
segments (VLANs) exist and how they are logically connected.
Troubleshooting Switched Networks 77
?– Have a plan: Some problems and solutions are obvious; others are not.
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