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%SYS-$-P2_WARN: 1/Host <mac_address> is flapping between ports <mod#>/<mod#> and <mod#>/<port#> message is appearing in system log.

2948G switch (5.5.3 CatOS) is attached to Catalyst 2948G-L3 switch (the latest IOS ...120-14.W5.20 image) via Fast EtherChannel (4x10/100 links - 2/1-4) trunk (802.1q). IRB is in use on C2948G-L3.

All is working correctly untill the following message appears on the C2948G console:

Date/Time: %SYS-4-P2_WARN: 1/Host 00039f62500f is flapping between port 2/3 and port 2/2.

When this error message occurs, the communications drops !!! The MAC address in the above error message is the MAC address of one of the BVIs configured on C2948G-L3.

I tried this scenario with the C3548XL switch instead of C2948G and all works fine.

There is no HSRP configured in this case. There is no physical loops problem in this case. STP was not configured and is in its default state.

What can be a cause of the above described problem ?


Re: %SYS-$-P2_WARN: 1/Host <mac_address> is flapping between por

This message indicates that a MAC address is being learned on two ports at the same time on the same VLAN. All communication will stop to this MAC for 15 seconds upon receiving this message. This message is generally an indication of a Layer 2 or Spanning-Tree loop. It this specific circumstance, it appears there is a failure with FastEtherchannel between the 2 switches.

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