Cisco – Does 2504 WLC support LAG

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I am finding some contradictions in Cisco documentation about the LAG support in 2504 WLC. On one hand, the Cisco 2500 Series Wireless Controller Deployment Guide clearly states:

Note: Link Aggregation (LAG) is not supported on the Cisco 2500 Series
Wireless Controller.

On the other hand, the brochure Cisco Wireless LAN Controllers at a glance states 2504 does support LAG.

After some search, I have found the bulletin for Cisco Unified Wireless Network Software Release 7.4 stating:

Wireless Controllers 8500, 2500, and Flex 7500 now support Link
Aggregation Group (LAG).

What makes me think the LAG support in the 2504 would be depending on the software version loaded on the device.

Since the only 2504 I can work on is having 7.2 software version and is in a production environment (not easy to upgrade and test on it), I still wonder:

  1. Does the 2504 WLC really support LAG?
  2. Does it require a minimum software version or any additional hardware for it?
  3. Is it having any limitation or is the same LAG functionality as in 5500 WLC series?

Best Answer

Yes, the 2504 supports LAG in v7.4. Your first guide refers to v7.0.116.0 and the second guide written in 5/2013 implies v7.4. Enabling LAG requires a reboot of the WLC and has limitations similar to the 5500.

When LAG is enabled on a WLC, the WLC forwards data frames on the same port on which they were received. The WLC relies on the neighbor switch to load-balance traffic across the EtherChannel. The WLC does not perform any EtherChannel load-balancing on its own.

Limitations/Restrictions, same as 5500 but note 5508 doesn't have ap-manager inf's:

  • LAG requires the EtherChannel to be configured for 'mode on' on both the controller and the Catalyst switch.
  • The load-balancing method configured on the Catalyst switch must be a load-balancing method that terminates all IP datagram fragments on a single controller port. Not following this recommendation may result in problems with access point association.
  • The recommended load-balancing method for Catalyst switches is src-dst-ip (enter the port-channel load-balance src-dst-ip command).
  • With LAG, all of the controller ports need to connect to the same neighbor switch. If the neighbor switch goes down, the controller loses connectivity. With multiple AP-manager interfaces, you can connect your ports to different neighbor devices. If one of the neighbor switches goes down, the controller still has connectivity. However, using multiple AP-manager interfaces presents certain challenges when port redundancy is a concern.
  • Port mirroring is not supported when link aggregation (LAG) is enabled on the controller.
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