System information

Troubleshooting Transparent Bridging Environments 20-427
Transparent Bridging: No Connectivity
Input and output queues full Excessive multicast or broadcast traffic can cause input and output queues to
overflow, resulting in dropped packets.
Step 1 Use the show interfaces command to look for input and output
drops. Drops suggest excessive traffic over the media. If the current
number of packets on the input queue is consistently at or greater
than 80% of the current size of the input queue, the size of the input
queue may require tuning to accommodate the incoming packet rate.
Even if the current number of packets on the input queue never
seems to approach the size of the input queue, bursts of packets may
still be overflowing the queue.
Step 2 Reduce broadcast and multicast traffic on attached networks by
implementing bridging filters, or segment the network using more
internetworking devices.
Step 3 If the connection is a serial link, increase bandwidth, apply priority
queuing, increase the hold queue size, or modify the system buffer
size. For more information, refer to Chapter 15, “Troubleshooting
Serial Line Problems.”
Host is down
Step 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.
Step 2 If any expected end nodes are missing, check the status of the nodes
to verify that they are connected and properly configured.
Step 3 Reinitialize or reconfigure end nodes as necessary and reexamine the
bridging table using the show bridge command.
1 MAC = Media Access Control
2 LSAP = Link Service Access Point
Possible Causes Suggested Actions