WLC Port Channel Host Flapping

[mark shuford]

Hello,

I have setup LAG for one of our 5508 controllers and have connected 4 of the 8 ethernet ports to a 4507 switch. After configuring 2 port channels on the switch we are receiving a host flapping error between the port channels and it seems to be causing a serious slowdown on the switch. When I shutdown one of the port channels the error goes away and traffic returns to normal. I have the same configuration at other locations with the only difference being the switches used are 3750G-12S and I do not see the host flapping error. It appears to only be a problem with modular switches.

One other thing of note: I read a Cisco white paper on LAG and it suggested creating the port channels over 2 different modules. For example, put ports G4/24 and G5/24 in port channel 1 and G4/25 and G5/25 in port channel 2. I tried this but I still got the host flapping error.

I searched the forum and found a few threads on the subject but no resolution. Any insight on a fix will be greatly appreciated.

Thanks

Mark

[Stephen Rodriguez]

Mark,

     Just to double check.  You configured two port channels on the switch, and connected these to the WLC?

If that is the case, that is currently not a supported config.  You can split the ports across the modules, but you can't link two different etherchannels to the WLC.

HTH,

Steve

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[mark shuford]

Thanks for the response Steve.

So you are saying that all 4 of the ports that I used from the controller should be assigned to one port channel on the switch?

Thanks

Mark

[Stephen Rodriguez · Accepted solution]

That is correct.  One port channel on the switch, but the ports can be across multiple blades.

HTH,

Steve

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Please remember to rate helpful posts or to mark the question as answered so that it can be found later.

[mark shuford]

Thanks for the help Steve. I have rated your post and and marked the question answered.