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Difficulty: HardWLAN Infrastructure Connections and LAG

A network engineer is implementing Link Aggregation (LAG) using IEEE 802.3ad LACP between a Cisco Catalyst 9800 Series Wireless Controller and an upstream Cisco Catalyst 9300 switch stack. Place the following implementation and verification steps in the correct chronological order required to establish the infrastructure link.

  1. 1Configure the physical switch interfaces connected to the controller uplink ports using 'channel-group 10 mode active'.
  2. 2Configure the created switch 'interface Port-channel 10' as an 802.1Q trunk, setting the native VLAN and allowed VLAN list.
  3. 3Configure the uplink interfaces on the Cisco Catalyst 9800 WLC into the matching EtherChannel uplink port bundle.
  4. 4Issue 'show etherchannel summary' on the switch stack to confirm the channel group status indicates 'SU' and physical ports show status 'P'.
  5. 5Confirm IP reachability to the WLC management IP and verify that Lightweight Access Points re-establish CAPWAP control and data tunnels.

Answer

The correct implementation sequence begins with configuring the physical switch interfaces with LACP mode active, configuring trunking parameters on the resulting switch Port-channel interface, configuring the WLC uplink EtherChannel bundle, verifying Layer 2 bundle operation with 'show etherchannel summary', and finally validating WLC management reachability and CAPWAP tunnel stability.
Establishing a Link Aggregation connection between a Cisco Catalyst 9800 WLC and an upstream switch requires a structured bottom-up approach. First, physical switch ports must be assigned to the LACP channel group ('channel-group 10 mode active'). Second, the resulting logical Port-channel interface must be configured with 802.1Q trunking and VLAN parameters. Third, the controller-side interfaces must be bundled into the corresponding uplink EtherChannel. Fourth, the engineer must verify Layer 2 LACP negotiation using 'show etherchannel summary' to ensure the channel state is 'SU' and member interfaces display 'P'. Finally, end-to-end control plane operation is verified by testing WLC management reachability and AP CAPWAP tunnel stability.

Step-by-Step Solution

1
Define switch member ports
Physical switch ports are associated into channel-group 10 using active LACP negotiation.
Assigning physical member ports creates the logical Port-channel interface on the switch.
2
Configure switch Port-channel interface
The Port-channel interface is set to switchport mode trunk with designated native and allowed VLANs.
Applying trunk configuration to the logical Port-channel ensures consistent trunking behavior across all bundled physical member links.
3
Configure WLC uplink LAG bundle
Controller physical ports are grouped into an uplink EtherChannel bundle.
With the switch ready to negotiate, the controller side is enabled for link aggregation.
4
Verify EtherChannel protocol status
Switch CLI displays 'SU' (Layer 2, In-use) for Port-channel 10 and 'P' (Bundled) for all member ports.
Verifying LACP status ensures physical links negotiated properly without misconfigurations such as mode mismatches or suspended ports.
5
Verify network access and CAPWAP operation
Management traffic reaches the WLC IP and AP CAPWAP tunnels operate successfully over the aggregated link.
End-to-end verification validates overall infrastructure connectivity and wireless control plane operation.

Key Concept

WLAN Infrastructure LAG and Switch EtherChannel Implementation Sequence
Estimated Time:2m 0s
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Topics

WLAN Infrastructure Connections and LAG

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