Cisco Wireless Controllers (WLC) support the configuration of Link Aggregation (IEEE 802.3ad – LAG) which bundles the controller ports into a single port channel. This helps simplify the configuration of the WLC interface ports, increase available bandwidth between the wireless and wired network, provide load-balancing capabilities between physical WLC ports and increase port redundancy.
To learn more about WLC interfaces refer to our article Cisco WLC Interfaces, Ports & Their Functionality article
The diagram below shows an example of a WLC 2504 with ports P1 and P2 in a LAG configuration connecting to a Cisco Catalyst or Nexus switch. In the configuration below WLC ports P1 and P2 are aggregated to provide a total of 2Gbps bandwidth:
Let’s take a quick look of what’s covered:
- Link Aggregation Restrictions and Considerations
- Wireless Controller LAG Configuration – Enabling LAG
- Configuring Switch to Support Link Aggregation
While LAG is the preferred method of connecting the WLC to the network there however a number of restrictions we need to be aware of to ensure we don’t stumble into any unpleasant surprises.
- On 2504 and 3504 WLCs you can bundle all 4 ports into a single link.
- On 5508 WLC you can bundle up to 8 ports into a single link.
- Link Aggregation Control Protocol (LACP) or Cisco proprietary Port Aggregation Protocol (PAgP) are not supported by the WLC. Port-Channel members must be set unconditionally to LAG (shown in the configuration below).
- Only one LAG Group is supported per WLC, you can therefore connect a WLC only to one switch unless using VSS (Catalyst) or vPC (Nexus) technologies.
- When LAG is enabled, if a single link fails, traffic is automatically switched to the other links.
- After enabling LAG the WLC must be rebooted.
- When enabling LAG, all dynamic AP manager interfaces and untagged interfaces will be deleted. (See related article WLC Interfaces – Logical Interfaces)
- After enabling LAG, all Virtual Interfaces use the LAG interface. No backup port (under the Virtual Interface settings) is configurable:
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