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DEMO: Link Aggregation on WLC

Link aggregation on a wireless LAN controller combines multiple physical ports into a single logical connection to increase bandwidth and provide redundancy. Configuration requires static port channel assignment on both the controller and the connected switch, as dynamic protocols like LACP and PAgP are not supported.

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About this video

A wireless LAN controller operating with a single uplink port creates a potential bottleneck under heavy traffic loads and a single point of failure if that link goes down. Link aggregation addresses both concerns by combining multiple physical Ethernet ports into one logical connection, increasing available bandwidth and providing redundancy. On a Cisco wireless LAN controller, this is enabled through the LAG mode setting found in the controller's general configuration tab, after which a reboot is required for the change to take effect. A critical consideration when implementing this configuration is that wireless LAN controllers do not support dynamic link aggregation negotiation protocols such as LACP or PAgP. Unlike switch-to-switch connections that can automatically negotiate and form port channels, the controller requires a static configuration on both ends of the link. The port channel on the connected switch must be set to always-on mode rather than using any automatic negotiation protocol, and the physical ports on the switch must be manually assigned to the aggregation group. Once both the controller and the switch are configured consistently and the physical connections are in place, the bundled link becomes fully operational.

What you'll learn

What's covered

WLC Link Aggregation

Aligned to

Cisco CCNA
2.4 Configure and verify Layer 2/Layer 3 EtherChannel (LACP)
2.7 Describe physical infrastructure connections of WLAN components
2.6 Describe Cisco Wireless Architectures and AP modes

Key terms

Link Aggregation Group
LAG
A bundle of multiple physical network links combined into a single logical link to multiply bandwidth and provide redundancy. Traffic is distributed across member links using a hashing algorithm based on source/destination MAC addresses, IP addresses, or port numbers.
Port Channel
The logical interface automatically created on a Cisco switch when physical interfaces are assigned to a channel group, used to apply shared configuration settings.
Bandwidth
The maximum rate of data transfer across a network path, typically measured in bits per second.
Redundancy
The duplication of critical components or systems to increase reliability and availability.
Switch
A network device that connects devices within a LAN and forwards traffic based on MAC addresses.
Wireless LAN Controller
WLC
A network device that provides centralized management of multiple lightweight wireless access points, handling functions such as client authentication, roaming, radio frequency management, and security policy enforcement. WLCs communicate with APs using CAPWAP and allow network-wide wireless configuration from a single management point.

Topics

Networking Link Aggregation Wireless Lan Controller Port Channel Wlan Network Redundancy

Transcript

Why Bundle the Ports

Up until now we've only been using one port on our wireless LAN controller. This could be problematic if we have a lot of traffic that's coming across it, or if that link goes down. Link aggregation lets us bundle the ports together to create more bandwidth to our wireless LAN controller and create redundancy.

Enabling LAG on the Controller

I have the web interface up for a wireless LAN controller. It shows the front end of it, and shows that we actually have four ethernet ports. These four ethernet ports act as switch ports, so we can actually plug APs into these, or other devices. However, in this case right now, what we want to do is link these four ports together and create a link aggregation port.

What I can do to do that is go under the controller, under the General tab, which is automatically on here, and I see this LAG mode on next reboot. I can select enable, apply this, save the configuration and do a reboot. The last thing that I need to make this happen is a reboot. Once this wireless LAN controller comes back up, these four ports will be linked together and will act as one port.

Why It Has to Be Always On

Some things you've got to keep in mind with this. We've already learned about lagpi and our LACP and PAgP — those are two automatic link aggregation protocols. What the switch can do is communicate with another switch to automatically set up a link aggregation and combine ports. Well, your wireless LAN controller can't do that, and so what we need to do is essentially set up these four ports to be statically assigned to a port channel.

What we have to do is the same thing on the switch. We can't have any kind of automated protocol set up to do that, so we have to specifically assign it on the switch so it's always on. The key to this is we want link aggregation always on, and not LACP or PAgP to set up these links automatically.

The other thing that I would need to do is go over to the switch, choose out four ports on the switch, and create that link aggregation group of always on — not LACP or PAgP on there, but just link aggregation, which is always on. Then I would connect all of the ports of this wireless LAN controller up to the four ports on the switch that I configured, and that would set up and finish this.

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