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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?
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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.
  • I have checked release notes for WLC software version 7.3.101.0 and 7.3.112.0 and both of them mark LAG as not supported yet in 2500 series. Could you please provide a reference reference for your statement about version 7.3? – Daniel Yuste Aroca Jun 6 '13 at 13:08
  • @DanielYusteAroca, I initially thought it was 7.4 where LAG was first added to the 2500, but then I found this in the 7.3 configuration guide: When you enable LAG on Cisco 2500 Series Controller to which the direct-connect access point is associated, the direct connect access point is disconnected since LAG enabling is still in the transition state. So perhaps this is only supported for direct-connect APs and not switches. cisco.com/en/US/docs/wireless/controller/7.3/configuration/…. In any case, point in answer revised. Thanks. – generalnetworkerror Jun 6 '13 at 18:14
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If you check in the 7.2 release notes it has the following limitations:

Features Not Supported on Cisco 2500 Series Controllers

•Wired guest access

•Cisco 2500 Series Controller cannot be configured as an auto anchor controller. However, you can configure it as a foreign controller.

•Bandwidth contract

•Access points in direct connect mode

•Service port

•Apple Talk Bridging

•LAG

The 7.4 release notes has LAG as supported:

What's New in This Release? This section provides a brief description of what is new in this release. For more information about instructions on how to configure these features, see the controller configuration guides published in the 7.4 Release category at http://www.cisco.com/en/US/products/ps10315/products_installation_and_configuration_guides_list.html.

•The Cisco Aironet 1600 Series Access Points are supported. For more information, see http://www.cisco.com/en/US/products/ps12555/index.html.

•Introduced support for the 802.11w standard as defined by the Management Frame Protection (MFP) service. Disassociation, Deauthentication, and Robust Action frames increase Wi-Fi network security by protecting the management frames from being spoofed.

•Increased scale for Cisco 2500 Series Controllers to support 75 access points and 1000 clients. Cisco 2500 Series Wireless LAN Controllers can now act as guest anchors and up to 15 EoIP tunnels are supported.

•Extended support for link aggregation (LAG) on the Cisco Wireless LAN 2500, Flex 7500, and 8500 Series Controllers. With this feature, you can aggregate multiple links to protect against link failures.

I'm not sure what limitation you are referring to? It seems it only supports mode on but that seems to be consistent for 5508 as well.

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