VLAN flapping

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Jan 11th, 2010
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Dear Concern,

There is a Cisco 4507 core switch and many networks are connected here. Recently a prolink BL680c server which has WS-CBS3020 in back panel is connected to core switch with multiple physical connections ( 10 connections between core switch and server , in server VMware is running ) specifying vlan 1 and 7. Now the network becomes slow and CPU utilization goes to high.

Please find the attachment file for log report and port configuration.

Please give me suggestion how to resolve this issue.


regards

skmdimran

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Giuseppe Larosa Mon, 01/11/2010 - 11:51
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Hello,


the error messages


18w2d: %SW_MATM-4-MACFLAP_NOTIF: Host 0201.0000.0000 in vlan 7 is flapping between port Gi0/2 and port Gi0/11
18w2d: %SW_MATM-4-MACFLAP_NOTIF: Host 0201.0000.0000 in vlan 7 is flapping between port Gi0/2 and port Gi0/11
18w2d: %SW_MATM-4-MACFLAP_NOTIF: Host 0201.0000.0000 in vlan 1 is flapping between port Gi0/16 and port Gi0/17
18w2d: %SW_MATM-4-MACFLAP_NOTIF: Host 0201.0000.0000 in vlan 7 is flapping between port Gi0/11 and port Gi0/10
18w2d: %SW_MATM-4-MACFLAP_NOTIF: Host 0201.0000.0000 in vlan 7 is flapping between port Gi0/2 and port Gi0/11


says that the server is using the links in active/active configuration.


To avoid to confuse the lan switch you need to use bundles of ports.

you can create two etherchannel bundles one made of 5 ports for vlan 1 and one made of 5 ports for vlan 7.


something like:


int gi4/x

switchport

switchport mode access

switchport access vlan 7

channel-group 7 active


on all 5 ports in vlan 7


int gi4/x

switchport

switchport mode access

switchport access vlan 1

channel-group 1 active


you can check if these etherchannel groups are free with

sh etherchannel summary


on blade switch

int gi0/y

switchport

switchport mode access

switchport access vlan 7

channel-group 7 active


on all 5 ports in vlan 7


int gi0/y

switchport

switchport mode access

switchport access vlan 1

channel-group 1 active





note: you need to do the same on the blade switch in this way you build two bundles and all the MAC address flapping confusion will end


Hope to help

Giuseppe

Hi Giuseppe,


Thanks for posting this. I am having the same issue on my 3750x switch and getting these messages. Can you please advise what can be done to address this.


003372: Sep 17 00:02:57.281: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/             17, changed state to up

003373: Sep 17 00:08:33.321: %SW_MATM-4-MACFLAP_NOTIF: Host 0026.c754.f76c in vlan 2 is flapping              between port Gi2/0/15 and port Gi1/0/13

003374: Sep 17 00:17:37.087: %SW_MATM-4-MACFLAP_NOTIF: Host 5c0e.8ba7.08c0 in vlan 2 is flapping              between port Gi2/0/15 and port Gi1/0/13

003375: Sep 17 00:19:09.488: %SW_MATM-4-MACFLAP_NOTIF: Host 000b.6cc9.e3f1 in vlan 2 is flapping              between port Gi2/0/15 and port Gi1/0/15

003376: Sep 17 00:25:25.893: %SW_MATM-4-MACFLAP_NOTIF: Host 5c0e.8ba7.0880 in vlan 2 is flapping              between port Gi2/0/15 and port Gi1/0/13

003377: Sep 17 00:29:54.077: %SW_MATM-4-MACFLAP_NOTIF: Host 000b.6cc9.093f in vlan 2 is flapping              between port Gi1/0/15 and port Gi2/0/15

003378: Sep 17 00:34:47.468: %SW_MATM-4-MACFLAP_NOTIF: Host 000b.6cc9.e3f1 in vlan 2 is flapping              between port Gi1/0/13 and port Gi1/0/15

003379: Sep 17 00:35:09.866: %SW_MATM-4-MACFLAP_NOTIF: Host 000b.6cc8.39cd in vlan 2 is flapping              between port Gi2/0/13 and port Gi2/0/15

003380: Sep 17 00:53:17.289: %SW_MATM-4-MACFLAP_NOTIF: Host 5c0e.8ba7.08c0 in vlan 2 is flapping              between port Gi2/0/15 and port Gi1/0/13

003381: Sep 17 00:53:20.771: %SW_MATM-4-MACFLAP_NOTIF: Host 5c0e.8ba7.094c in vlan 2 is flapping              between port Gi2/0/15 and port Gi2/0/13

003382: Sep 17 00:53:22.020: %SW_MATM-4-MACFLAP_NOTIF: Host 5c0e.8ba7.0944 in vlan 2 is flapping              between port Gi2/0/15 and port Gi1/0/13

003383: Sep 17 00:58:31.292: %SW_MATM-4-MACFLAP_NOTIF: Host 000b.6cc8.39cd in vlan 2 is flapping              between port Gi1/0/15 and port Gi2/0/15

003384: Sep 17 01:03:12.335: %SW_MATM-4-MACFLAP_NOTIF: Host 000b.6cc9.e3f1 in vlan 2 is flapping    


Many Thanks for your help.

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