One issue I’ve run into both in studying for the ccie wireless lab, and now in developing training material, is how to completely clear the configuration on a lightweight AP. In the “old” days, you would write erase the IOS configuration, reboot, and BAM – you had a clean slate to work from. However, the pesky LAPs keep the IP addresses of previously joined WLCs and other WLCs in the same mobility group in NVRAM. So, what do you do? There is that command, clear ap-config AP_Name that you can run from the CLI of the WLC, if it’s joined to a WLC.
And, that will clear the configuration in NVRAM. You can verify that with the “show lwapp client config command. The first is the before, and the second is the after (after it has rebooted).
(Cisco Controller) >clear ap-config LWAP1 clear ap-config will clear ap config and reboot the AP, Are you sure you want continue? (y/n) y All AP configuration including AP's static IP configuration has been cleared.
And, then, after the command is run
LWAP1#show lwapp client config ... (lines removed for ease of explanation) name LWAP1 mwarName WLC1 mwarName WLC2
So, now, you have a clean config. Or, mostly clean. You can use various methods to have the AP discover a WLC (DNS, DHCP, broadcast), but you still cannot statically define information from the CLI. Go ahead. Try lwapp ap controller ip address x.x.x.x or clear lwapp private-config. You will get the infamous ERROR!!! Command is disabled. error message.
AP001d.a1ec.11cc#show lwapp client config AP001d.a1ec.11cc#
But, wasn’t the configuration cleared??? Mostly yes. However, the image file used to boot the AP after the config was cleared is the full LWAPP image that it was last using. It uses the information in the flash:env_vars file in order to boot using that information.
AP001d.a1ec.11cc#lwapp ap controller ip address 10.10.111.20 ERROR!!! Command is disabled.
The other pieces should look familiar as well, to those who have used the local TFTP method of converting from LWAPP to IOS. Because of using a full LWAPP image, the AP knows that at one point it was joined to a WLC. If it was joined to a WLC, then the lwapp commands shouldn’t be used.
AP001d.a1ec.11cc#more flash:env_vars BOOT=flash:/c1130-k9w8-mx.124-10b.JDD/c1130-k9w8-mx.124-10b.JDD DEFAULT_ROUTER=10.0.0.1 ENABLE_BREAK=no IP_ADDR=10.0.0.1 MANUAL_BOOT=no NETMASK=255.255.255.224 RELOAD_REASON=9 TERMLINES=0
So, how do we get around this? The simplest way I have found is to treat the AP as if you were going to do a local TFTP upgrade, but without the TFTP server. If you power down the AP and then hold the Mode button until it turns red (about 20 seconds), the AP will boot up. If you look at the console, you will see the following:
Looks like a TFTP upgrade. Then, when the TFTP transfer times out, the AP gives an error message %Error opening long_file_name. After this, it shows:
button pressed for 20 seconds process_config_recovery: set IP address and config to default 10.0.0.1 process_config_recovery: image recovery image_recovery: Download default IOS tar image tftp://255.255.255.255/c1130-k9w7-tar.default
Ah, the recovery image! After the AP boots, the flash:env_vars file no longer has that BOOT line.
Loading "flash:/c1130-rcvk9w8-mx/c1130-rcvk9w8-mx"...###############################[...] File "flash:/c1130-rcvk9w8-mx/c1130-rcvk9w8-mx" uncompressed and installed, entry point: 0x3000 executing...
Now, when we try the lwapp commands, they will be accepted. This is because it is the recovery image, not the full image. Let’s see what happens:
AP001d.a1ec.11cc#more flash:env_vars DEFAULT_ROUTER=10.0.0.1 ENABLE_BREAK=no IP_ADDR=10.0.0.1 MANUAL_BOOT=no NETMASK=255.255.255.224 RELOAD_REASON=9 TERMLINES=0
So, the lwapp command was accepted, and now we can statically define the WLC for it to discover. While you probably won’t have to do this on the lab (though, who knows!) hopefully it can be useful in the field or in your home lab.
AP001d.a1ec.11cc#lwapp ap controller ip address 10.10.111.20 AP001d.a1ec.11cc# examining image... Loading file /c1130... ! extracting info (292 bytes) Image info: Version Suffix: k9w8-.124-10b.JDD Image Name: c1130-k9w8-mx.124-10b.JDD Version Directory: c1130-k9w8-mx.124-10b.JDD Ios Image Size: 3645952 Total Image Size: 3645952 Image Feature: WIRELESS LAN|LWAPP Image Family: C1130 Wireless Switch Management Version: 18.104.22.168 Extracting files... c1130-k9w8-mx.124-10b.JDD/ (directory) 0 (bytes) extracting c1130-k9w8-mx.124-10b.JDD/c1130-k9w8-mx.124-10b.JDD (3374566 bytes) *Mar 1 0!0:08:23.897: %LWAPP-5-CHANGED: LWAPP changed state to JOIN *Dec 2 23:38:41.161: %LWAPP-5-CHANGED: LWAPP changed state to IMAGE!!