Excess Defer Frames – Understanding Show Interface gix/x/x Controller Output

Unless someone is clearing counters you should never see any odometer-type counters (those that increment based on a packet action) decrease, they should always increase. That part sounds like a bug.

As far as what causes output drops in particular, there are so many different causes that it's very difficult to pinpoint it exactly. Sometimes there is congestion inside the switch's backplane and those might show up as output drops on the outgoing interface. In rare circumstances you can also get microbursts that don't show up when polled at 1 minute intervals that quickly overload the interface, but then drop back down very quickly. I would suggest grabbing the SNMP OID for output drops and then graphing that and see how it corresponds to the CLI counter.

Generally speaking, you don't want any output drops as they indicate a packet that did not make it to its destination. But, if you're running your links hot (which you say you're not) they're unavoidable to an extent, mostly due to interior switch buffering, etc.

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.