Wireless Q&A: Clearing Saved Controllers from a LAP

Question: I am in the process of moving a LAP to another network, but it only remembers the old controllers it was connected to. Can I clear previously saved controllers from my LAP?

Answer:

During the discovery process, the Wireless LAN Controller (WLC) and the Lightweight Access Point (LAP) play a game of hide and seek. If you don’t tell the LAP where the WLC is, it won’t know where the WLC is in the network. To find a WLC, the LAP sends discovery requests to the controller through various discovery algorithms:

  • DHCP option 43
  • DNS
  • Layer 3 broadcast
  • OTAP
  • static

Once the LAP learns about WLCs on the network, it remembers them and stores it in NVRAM. Depending on the mobility group size and controller version, it can store up to 24 WLCs it previously discovered. This can be a problem if you have to move the LAP. It will use the previously discovered WLCs in its memory to find a WLC to connect to. You can Clear ALL Configs from the GUI, but the LAP still remembers previously known controllers.

A better way to clear the configuration is to login to the LAP console and use the debug lwapp console cli command and then issue the erase /all nvram command to clean NVRAM completely. If you are running 5.2 or newer software code of the WLC, replace lwapp with capwap.

Author: David Cutright, GigaWave Technologies

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1 comment

  1. Scott Fella Reply

    I just couldn’t remember the command from what you mentioned in the CUWM class.