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[Archive] [WLC] WLC does not tunnel (look for a VLAN) elsewhere if its local instance of the VLAN is down



Article ID: KB29608 KB Last Updated: 10 Oct 2020Version: 2.0

A WLC does not search for an active instance of a VLAN in a Mobility-Domain or Network-Domain if its own local instance of the concerned VLAN is down. This causes users to lose connectivity. This article explains the reason for this behavior and describes the warnings logged in the buffer log.


Existing/New client session requesting access to a particular VLAN loses connectivity.


This situation occurs when a local instance of a VLAN on a WLC goes down. 


Network admins may expect that the Mobility-Domain / Network-Domain feature set will cover this with tunnels created from the concerned WLC to other WLCs/APs where the VLAN exists. However, by design, if a local client VLAN is in DOWN state on a WLC for any reason, all existing and new client sessions using/requesting that VLAN will face connectivity issues.

Tunnels are only created from a WLC if the intended client VLAN DOES NOT EXIST on the concerned WLC but exists elsewhere in the Mobility Domain.

Messages are logged in the buffer log, indicating that a VLAN is unavailable. This message appears at severity WARNING. Subsequent sm and dot1x traces for debugging will indicate problems with the VLAN as well. These logs will alert admins to the problem so that they can quickly isolate it.

Modification History:
2020-10-10: Archived article.
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