Redundant Wireless Access Points

In both wired and wireless campus LAN architectures, redundancy is usually desirable to ensure high availability. For campus networks with WLANs that are mission critical, Cisco has a feature called access point hot standby that supports two access points being configured to use the same channel in a single coverage area. Only one of the access points is active. The standby access point passively monitors the network and the primary access point. If the primary access point fails, the secondary access point take over to provide coverage.

NOTE

Don't confuse access-point hot standby with Cisco's Hot Standby Router Protocol (HSRP), which is covered in the "Workstation-to-Router Redundancy" section. Access-point hot standby addresses Layer 2 redundancy, whereas HSRP addresses Layer 3 redundancy.

You should place the standby access point near the access point it will monitor and give it the same configuration (except for a different IP address). The standby access point associates with the monitore access point as a client and queries the monitored access point regularly through both the Ethernet interface and the RF interface. If the monitored access point fails to respond, the standby access point becomes active, signals the primary access point radio to become quiescent, and takes the monitored access point's place in the network.

As soon as the primary access point failure is detected, user intervention is required. The user should return the backup access point to standby mode. Failure to reset the standby access point results in bo' the primary and standby access points operating concurrently on the same channel when the primary access point comes back online.

Continue reading here: Redundancy and Load Sharing in Wired LANs

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