Information Technology Reference
In-Depth Information
Table 20-2 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table20-2 Transparent Bridging: No Connectivity
Possible Causes
Suggested Actions
Hardware or
media problem
has occurred
1.
Use the
show bridge
exec command to see whether there is a
connectivity problem. If there is, the output will not show any
MAC
1
addresses in the bridging table.
2.
Use the
show interfaces
exec command to determine whether
the interface and line protocol are up.
3.
If the interface is down, troubleshoot the hardware or the
media. Refer to Chapter 3, “Troubleshooting Hardware and
Booting Problems.”
4.
If the line protocol is down, check the physical connection
between the interface and the network. Make sure that the
connection is secure and that cables are not damaged.
If the line protocol is up but input and output packet counters are
not incrementing, check the media and host connectivity. Refer to
the media troubleshooting chapter that covers the media type used
in your network.
Host is down
1.
Use the
show bridge
exec command on bridges to make sure
that the bridging table includes the MAC addresses of
attached end nodes.
The bridging table comprises the source and destination MAC
addresses of hosts and is populated when packets from a source or
destination pass through the bridge.
2.
If any expected end nodes are missing, check the status of the
nodes to verify that they are connected and properly
configured.
3.
Reinitialize or reconfigure end nodes as necessary, and
re-examine the bridging table using the
show bridge
command.
Bridging path is
broken
Identify the path that packets should take between end nodes.
If there is a router on this path, split the troubleshooting in
two parts: node1-router and router-node2.
1.
Connect to each bridge on the path, and check the status of the
ports that are used on the path between end nodes, just as
described in the previous discussion on a hardware or media
problem.
2.
Using the
show bridge
command, check that the MAC
address of the nodes are learned on the correct ports. If not,
there may be instability on your Spanning Tree topology. (See
Table 20-2.)
3.
Check the state of the ports using the
show span
command.
If the ports that should transmit traffic between the end nodes
are not in the forwarding state, the topology of your tree may
have changed unexpectedly. (See Table 20-3.)
4.
