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[WLC] Configuring web-portal-session-timeout with respect to DHCP lease time



Article ID: KB29610 KB Last Updated: 07 Mar 2016Version: 2.0

Stale session retention can cause the WLC to assign a DHCP lease to a new client before the old client has been released. This article recommends how to configure the web-portal-session-timeout knob so as to keep a web-portal session alive for a client.


The web-portal-session-timeout knob lets the WLC keep a web-portal session alive for the configured timeout value after the specific client has moved out of coverage area. If the value of the knob exceeds a certain value in proportion to the DHCP lease time, a new client may obtain the same IP address for which the WLC has retained a stale session for the former client. This can cause trouble for the new client, who may not obtain a web login page to authenticate.



The web-portal-session-timeout value should never exceed half of the configured DHCP lease time for clients. This is because clients usually renew a DHCP lease half way through the lease time. Even if a client left the network at just before the halfway point of the lease time, without renewing the lease, the web-portal-session-timeout only kicks in for the remaining half time at the maximum.

This allows the system to clean up the session just before the lease expires, and the DHCP server can then be ready to hand out the same IP address to another user. In addition,the WLC does not keep stale session data for more than one DHCP lease duration.

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