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New Member

12.2(25)EWA4 Network loops

Has anyone ever experienced any bugs within IOS 12.2(25)EWA4 in relation to network loops?

I have read the following; but we do not have loopguard enabled (yet) and when we suffered the problem I am not aware of any ports than were shutdown and no shutdown-ed.

A port enabled for Loop Guard that participates in spanning tree (and is in BLK state) goes into a loop inconsistent state when it stops receiving BPDUs from its neighbor. When the neighbor resumes sending BPDUs (instead of STP BPDUs), STP ordinarily recovers from this state. For this caveat, STP does not recover and the port remains stuck.


-Enter the shut and no shut commands on the port.

-Disable Loop Guard on the port and then re-enable it. (CSCsc04047)

•A Catalyst 4500 series switch with Supervisor Engine IV running Cisco IOS Release 12.2(25)EWA3 will send an ARP packet (from an STP blocking port) that can cause a broadcast storm when you either reload a Catalyst 4500 series switch with a blocking port or enter shut and no shut commands on any port of the switch

Any ideas?

New Member

Re: 12.2(25)EWA4 Network loops

The messages we receive are as follows; and seem to originate with VLAN 1 traffic.

Cold start - 359580282 CISCO-SYSLOG-MIB::clogMessageGenerated "C4K_EBM" 5 "HOSTFLAPPING" "Host 00:0C:30:32:B7:FF in vlan 1 is flapping between port Gi1/1 and port Gi1/2" 359580282

I have ruled out rogue switches, cabling and mis-config in this case and am looking towards a IOS bug.