Cisco Catalyst 4000 series Hardware Troubleshoot page 9

Getting continuous %PAGP−5 left/joined bridge messages
Complete these steps:
1. Capture the show port <mod/port>, show mac <mod/port>, and show spantree summary
command output.
System messages similar to these messages are informational, although if the errors continue to
repeat, the link can be flapping.
2002 Jan 19 14:59:05 %PAGP−5−PORTFROMSTP:Port 2/11 left bridge port 2/11
2002 Jan 19 14:59:23 %PAGP−5−PORTTOSTP:Port 2/11 joined bridge port 2/11
2. If these messages occur repeatedly on certain ports, refer to these document for possible causes:
♦
Common CatOS Error Messages on Catalyst 4000 Series Switches
♦
Common CatOS Error Messages on Catalyst 5000/5500 Series Switches
♦
Common CatOS Error Messages on Catalyst 6000/6500 Series Switches
3. If you also see errors on the port in the show port <mod/port> and show mac<mod/port> command
output, see the Seeing errors on the ports section for troubleshooting steps.
4. Issue the show spantree summary command in order to verify how many ports are in each VLAN, if
any ports on the switch are blocking, and which VLANs are being blocked. Since Spanning−Tree
Protocol (STP) loops can cause link flaps or actually bring down a switch or network, with the
appearance of a hardware failure, this is vital information to capture, whether troubleshooting
hardware or software. Refer to LAN Technical Tips for more information on how to troubleshoot
STP.
Can not autonegotiate or speed/duplex mismatch
Complete these steps:
1. Make sure you have speed and duplex configured identically on both sides of the link. Catalyst 4000
switchports are set to auto by default. When both sides of a 100 BaseTX link autonegotiate correctly,
the show port <mod/port> command output is as follows:
Duplex
−−−−−−−
a−full
Hardcode both sides. Remember when hardcoding the port, the port speed must be set first and then
the duplex setting must be set. Issue the show port <mod/port> command. The switch output is as
follows:
Duplex
−−−−−−−
full
Note: Even though the switch has been hard coded, the connecting device must still be hardcoded to
eliminate problems.
2. If there is an autonegotiation problem caused by a speed/duplex mismatch or NIC incompatibility,
errors show up on the ports. Refer to these documents for more information:
♦
Configuring and Troubleshooting Ethernet 10/100Mb Half/Full Duplex Auto−Negotiation
♦
Troubleshooting Cisco Catalyst Switches to NIC Compatibility Issues
Speed
−−−−−−−
a−100
Speed
−−−−−−−
100