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Community Member

Issue with duplicate MAC enteries causing port flapping when wireless roaming

I have multiple wireless access points plugged into a 3560X.  When the wireless clients begin roaming they cause duplicate MAC enteries to be created and this causes the switch ports to flap.  Is there a way to configure the switch to either ignore the duplicate MAC enteries on the switchports that have been connected to the APs or is there a way to have the ARP tables update and resolve the conflicting MAC enteries with out causing the switchport to flap?

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VIP Purple

Issue with duplicate MAC enteries causing port flapping when wir

Hi Andrew,

If your APs are just bridging clients from the wireless right onto your wired network, then you're going to see this from time to time. Clients will appear from different ports as they re-associate to other APs/cells in the ESSID.

Hope it helps.

Regards

9 REPLIES
Bronze

Issue with duplicate MAC enteries causing port flapping when wir

Do you by any chance have layer 3 roaming? By this I mean do the clients roam against different subnets. Hence do they acquire IP addresses on different subnets?

Community Member

Issue with duplicate MAC enteries causing port flapping when wir

No the APs are all in the same subnet so the clients will keep the same IP address. 

Community Member

Issue with duplicate MAC enteries causing port flapping when wir

I'm looking into lowering the address ageing time but not sure this is exactly the solution that I am looking for.  This is going to cause more ARP traffic for addresses that haven't moved causing a delay in connectivity for those clients.  It's a stop gap solution I assume. 

Community Member

Issue with duplicate MAC enteries causing port flapping when wir

were you able to resolve this? I am having a similar issue using Motorola AP's and cisco switches.

VIP Purple

Issue with duplicate MAC enteries causing port flapping when wir

Hi Andrew,

If your APs are just bridging clients from the wireless right onto your wired network, then you're going to see this from time to time. Clients will appear from different ports as they re-associate to other APs/cells in the ESSID.

Hope it helps.

Regards

Community Member

Issue with duplicate MAC enteries causing port flapping when wir

Being that this is only coming from one mobile unit. I believe you may be right on that one Sandeep.

Community Member

Hi, could you solve it? I

Hi, could you solve it? I have Motorola AP´s and cisco switches too.

I was thinking to try with lowering the address ageing time...

VIP Purple

Re: Issue with duplicate MAC enteries causing port flapping when

Hi Deven,

I believe your APs are in Autonomous mode. Is that correct ?

In unified wireless, roaming should be smooth & should not cause MAC flapping when user roam from one AP to another

HTH

Rasika

*** Pls rate all useful responses ****

It sounds like you're just

It sounds like you're just receiving mac-move notifications, however the clients should still be operating properly.  Since these clients will be "moving", per design, you may just want to disable mac-move notifications.  This shouldn't cause "duplicate" entries.  The switch can only have a standard client Mac Address in 1 port in the CAM table at a time, otherwise you would have a loop.  Also, this shouldn't play in to ARP, because the L3 SVI should still have the same ARP (mac->IP) even when the devices shows connected through a new AP/Switchport.

Disable mac-move notifications

 

no mac address-table notification

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