Explains how Multi-LAGs provide high availability and increased bandwidth by aggregating multiple network links across different devices.
Multichassis link aggregation group
A multichassis link aggregation group (multi-LAG) is a switch interconnection technology that:
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Connects multiple controller uplinks to separate uplink switches for redundancy and load balancing.
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Supports VLAN-based traffic splitting when connected to a multiswitch topology.
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Provides the ability to distribute traffic on different uplinks, based on VLANs. For example, guest traffic can be completely isolated to a different switch or network from the enterprise network. You cannot configure the same VLAN on both uplinks.
Starting with Cisco IOS XE Amsterdam 17.2.1, the multichassis link aggregation group (multi-LAG) feature, which provides flexibility in connecting the controller to a switch's infrastructure, is supported.
You can connect a LAG to a single switch. However, different VLANs is connected to different LAGs. The redundancy port is connected to the same distribution switch as the uplinks or directly connected in a back-to-back configuration.
Multi-LAG is supported in LAG ON mode, LACP, and PAgP modes.
Prerequisites for Multi-LAG
To ensure optimal performance and avoid configuration conflicts:
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Connect each LAG to a single switch.
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Assign different VLANs to different LAGs.
Restrictions for Multi-LAG
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Automatic failover from the primary LAG to the secondary LAG is not supported if the primary LAG fails.
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The interface on the controller does not come up when you shut or unshut the associated switch port.
This restrictions is specific to Cisco Catalyst 9800-CL Cloud Wireless Controllers deployed in KVM environments using SR-IOV.
Supported topologies
Supported topologies are network deployment configurations. They define how Cisco Catalyst 9800 series controllers connect with the network through their available ports and set limitations regarding mixing port types and minimum group sizes for link aggregation.
The Cisco Catalyst 9800-80 Wireless Controller has eight ports, while the Cisco Catalyst 9800-40 and Cisco Catalyst 9800-L wireless controllers have four ports each. Multi-LAGs can only include ports with matching capabilities, such as 2.5 G with 2.5 G, or 10 G with 10 G ports. You cannot include both a 2.5 G port and a 10 G port in a port channel group. Each group must have a minimum of two ports in one LAG.
