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CAPWAP teardown?

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Oct 11th, 2013
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Hi All,


Need help to understand how the CAPWAP tunnel work when one in the bundled (group of 4) port from portchannel group was shutdown.


Here's the logical diagram


APs <-> Access Switch <-portchannel-> Distri Switch <-portchannel-> Core Switch <-portchannel-> WLC


1 of 4 bundled uplink ports in portchannel shown in RED text was shutdown deliberately during this time the Prime Infra 1.3 reports that APs was disassociated from the controller and 1 minute later Prime Infra reports that the APs was now associated to the controller without touching any devices.


Is this a normal behaviour of a CAPWAP? If not then, what should I do?


Regards,


Dave



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Rasika Nayanajith Tue, 10/15/2013 - 15:40
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What is the load-balancing mechanism of your switch etherchannels ? "show etherchannel load-balance" should tells you this.


If AP to WLC capwap traffic went through the interface you shutdown, then there is possibility your AP lost connectivity to WLC momentarily. But should not take that long to revert traffic to any other interfaces.


You can do a test like this. Enable Telnet for one your AP (via WLC GUI : Wireless -> select your AP -> Advanced -> tick Telnet checkbox). Then telnet to AP & ping your WLC IP from there. Then shutdown one of your (out of 4)  your switch etherchannel interface & see whether you will see ping drops for short period of time). If packet drops see how many drops before getting the connectivity back.


HTH

Rasika


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Dave Anthony David Tue, 10/15/2013 - 19:36
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DS1#sh etherchannel load-balance

EtherChannel Load-Balancing Configuration:

        src-dst-ip


EtherChannel Load-Balancing Addresses Used Per-Protocol:

Non-IP: Source XOR Destination MAC address

  IPv4: Source XOR Destination IP address

  IPv6: Source XOR Destination IP address


AS1#sh etherchannel load-balance

EtherChannel Load-Balancing Configuration:

        src-dst-ip


With this, can you confirm if this is the default behaviour of CAPWAP when traversing etherchannel ports?

Rasika Nayanajith Tue, 10/15/2013 - 20:56
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This is the preferred load balancing method you should use. This will help AP<-----> WLC traffic always goes through the same physical link of your ether channel.


To confirm what happen to ap registration, you have to do a test like I mentioned earlier & get the AP console output while your are doing this test. It will prove whether AP disassociate when a physical interface goes down in a etherchannel which carry the CAPWAP traffic.



HTH

Rasika


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kaaftab Tue, 10/15/2013 - 16:34
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Considering the scenario provided that is due to the ether-channel configuration 

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