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having a weird issue with a cisco 3550-48.   ios ver

12.2(52)


It is a remote site that has one trunk port going to it on port 48, ports 1,2,and 3 are all access ports.


at random times i drop pings to devices attached to 1,2 and 3 similtaneously, typically 1-3 packets, then the ports all come back up at the same time.


I am running RSTP and with STP logging enabled I do recieve the following messages:

1d22h: %SPANTREE-5-TOPOTRAP: Topology Change Trap for vlan 1
1d22h: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 1: New Root Port is FastEthernet0/48. New Root Mac Address is 0008.e3fd.4600
1d22h: %SPANTREE-5-TOPOTRAP: Topology Change Trap for vlan 12
1d22h: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 12: New Root Port is FastEthernet0/48. New Root Mac Address is 0008.e3fd.4600
1d22h: %SPANTREE-5-TOPOTRAP: Topology Change Trap for vlan 1
1d22h: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 1: New Root Port is FastEthernet0/48. New Root Mac Address is 0008.e3fd.4600
1d22h: %SPANTREE-5-TOPOTRAP: Topology Change Trap for vlan 12
1d22h: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 12: New Root Port is FastEthernet0/48. New Root Mac Address is 0008.e3fd.4600
1d22h: %SPANTREE-5-TOPOTRAP: Topology Change Trap for vlan 1
1d22h: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 1: New Root Port is FastEthernet0/48. New Root Mac Address is 0008.e3fd.4600

The root bridge is set and and a low priority, and none of my links are flapping.    

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rtjensen4 Thu, 08/19/2010 - 13:35
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Is the 3550 your STP root?

Also, do you know where this MAC address 0008.e3fd.4600 is?


If the 3550 is supposed to be your root, try to use

spanning-tree vlan 1,12 priority 4096

to ensure your switch stays as the root.


It looks almost like somthing's causing the STP to reconverge. Maybe try to enable bpduguard on the access-ports. If somthing connected the access-ports is spewing BPDUs for some reason, that could be causing the issues.


Interface Fa0/1

spanning-tree bpduguard enable


Are there any connectivity issues between the 3550 and whatever is connected on port 0/48? Errors on the port ? If for some reason there's latency, that could cause the RSTP times to time out before the messages are recieved.

no this 3550 is not the root, the mac address 0008.e3fd.4600 is the proper root bridge and is located out port 48.   I enabled  spanning tree bpdu filter enabled on access ports, and spanning tree bpdu guard as well with no success.    


also here is some more debugging messages i have recieved.


Output show spanningtree detail:

Number of topology changes 104 last change occurred 00:00:38 ago

          from FastEthernet0/8

  Times:  hold 1, topology change 35, notification 2

          hello 2, max age 20, forward delay 15

  Timers: hello 0, topology change 0, notification 0, aging 300


Debug output:

01:24:07: RSTP(12): Fa0/8 rcvd info expired

01:24:07: RSTP(12): updt roles, information on root port Fa0/8 expired

01:24:07: RSTP(12): we become the root bridge

01:24:07: RSTP(12): Fa0/8 is now designated

01:24:12: RSTP(1): Fa0/8 rcvd info expired

01:24:12: RSTP(1): updt roles, information on root port Fa0/8 expired

01:24:12: RSTP(1): we become the root bridge

01:24:12: RSTP(1): Fa0/8 is now designated

01:24:15: RSTP(12): updt roles, superior bpdu on Fa0/8 (synced=0)

01:24:15: RSTP(12): Fa0/8 is now root port

01:24:17: RSTP(1): updt roles, superior bpdu on Fa0/8 (synced=0)

01:24:17: RSTP(1): Fa0/8 is now root port

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