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ravindra Krishna
Beginner

%C4K_EBM-4-HOSTFLAPPING:

ts.jpg

Hi All,

I have the attached set up. I am reciving the following errors on my l3 switch

Dec 21 14:29:47.183: %C4K_EBM-4-HOSTFLAPPING: Host 00:1F:16:2C:EF:C8 in vlan 4 is flapping between port Gi4/7 and port Gi3/3
Dec 21 14:29:50.683: %C4K_EBM-4-HOSTFLAPPING: Host 70:5A:B6:B3:9A:41 in vlan 4 is flapping between port Gi4/7 and port Gi2/37
Dec 21 14:30:02.951: %C4K_EBM-4-HOSTFLAPPING: Host 00:1F:16:2C:EF:C8 in vlan 4 is flapping between port Gi4/7 and port Gi3/3
Dec 21 14:30:17.191: %C4K_EBM-4-HOSTFLAPPING: Host 00:1F:16:2C:EF:C8 in vlan 4 is flapping between port Gi3/3 and port Gi4/7
Dec 21 14:30:35.247: %C4K_EBM-4-HOSTFLAPPING: Host 00:1F:16:2C:EF:C8 in vlan 4 is flapping between port Gi4/7 and port Gi3/3
Dec 21 14:30:55.847: %C4K_EBM-4-HOSTFLAPPING: Host 00:1F:16:2C:EF:C8 in vlan 4 is flapping between port Gi4/7 and port Gi3/3
Dec 21 14:31:08.667: %C4K_EBM-4-HOSTFLAPPING: Host 00:23:24:0B:88:34 in vlan 4 is flapping between port Gi4/7 and port Gi3/5
Dec 21 14:31:17.215: %C4K_EBM-4-HOSTFLAPPING: Host 00:23:24:0B:88:34 in vlan 4 is flapping between port Gi4/7 and port Gi3/5
Dec 21 14:31:19.771: %C4K_EBM-4-HOSTFLAPPING: Host 00:1F:16:2C:EF:C8 in vlan 4 is flapping between port Gi4/7 and port Gi3/3
Dec 21 14:31:50.671: %C4K_EBM-4-HOSTFLAPPING: Host 70:5A:B6:B3:9A:41 in vlan 4 is flapping between port Gi4/7 and port Gi2/37
Dec 21 14:31:57.167: %C4K_EBM-4-HOSTFLAPPING: Host 00:23:24:0B:88:34 in vlan 4 is flapping between port Gi3/5 and port Gi4/7
Dec 21 14:32:08.675: %C4K_EBM-4-HOSTFLAPPING: Host 00:23:24:0B:88:34 in vlan 4 is flapping between port Gi4/7 and port Gi3/5
Dec 21 14:33:50.807: %C4K_EBM-4-HOSTFLAPPING: Host 00:1F:16:2C:EF:C8 in vlan 4 is flapping between port Gi4/7 and port Gi3/3
Dec 21 14:34:13.067: %C4K_EBM-4-HOSTFLAPPING: Host 00:1C:25:A1:42:46 in vlan 4 is flapping between port Gi4/7 and port Gi2/3
Dec 21 14:34:40.299: %C4K_EBM-4-HOSTFLAPPING: Host 00:1F:16:2C:EF:C8 in vlan 4 is flapping between port Gi4/7 and port Gi3/3

I searched the goodle

https://supportforums.cisco.com/docs/DOC-2116

Please check the third point the HUB/bridge device.  Please let me know how to resolve this issue. Any assitance wil be appreciated.

Cheers!

RK

1 REPLY 1
dixho
Frequent Contributor

the error message means that the switch learns the same MAC address  on two different ports. Usually, it means that there is a loop not  blocked by spanning tree.The problem seems to be caused by gig 4/7 as  gig 4/7 is shown in all  %C4K_EBM-4-HOSTFLAPPINGerror messages.

I do not 100% understand the network topology. I understand that there is a firewall configured with bridging mode on gig 4/7  on the CAT4500. Usually, it means that the firewall bridges traffic  between VLAN 4 and 999. I do not understand why the CAT4500 loop traffic  on VLAN 4 back. You should look at other switches and find out where  the loop is.