Cisco Cisco 2106 Wireless LAN Controller

The 1250 series access points may contain either an old bootloader or a new bootloader. Those with an 
old bootloader do not generate a crash log when a crash occurs. The crash log is disabled so that a crash 
does not corrupt the flash file system. Those with a new bootloader generate a crash log if the access 
point is running controller software release 4.2.112.0 or later.

New 1250 series access points shipped from the factory contain the new bootloader image, which fixes 
the flash file system after it is corrupted during a crash (without losing files). This new bootloader 
automatically sets a new CRASH_LOG environment variable to “yes,” which enables a crash log to be 
generated following a crash but only on controllers running software release 4.2.112.0 or later. 
Therefore, no user configuration is needed to enable a crash log on new 1250 series access points shipped 
from the factory.

In controller software release 4.2.61.0 and later, the controller’s bootup configuration file is stored in an 
Extensible Markup Language (XML) format rather than in binary format. When you upgrade a controller 
to 4.2.61.0 or a later software release, the binary configuration file is migrated and converted to XML.

You cannot download a binary configuration file onto a controller running software release 5.1.163.0. 
Also, do not attempt to make changes to the configuration file. If you do so and then download the file 
to a controller, the controller displays a cyclic redundancy checksum (CRC) error while it is rebooting 
and returns the configuration parameters to their default values.

When you upgrade to controller software release 5.0.148.0 or later, the LWAPP mode changes to Layer 
3 if it was previously configured for Layer 2. 

If you downgrade from controller software release 5.1.163.0 or 5.0.148.0 to 4.2.61.0 or an earlier release, 
the LWAPP mode changes from Layer 3 to Layer 2. Access points may not join the controller, and you 
must manually reset the controller to Layer 3 to resolve this issue.

Access points running recent Cisco IOS versions transmit multicast and management frames at the 
highest configured basic rate, which could cause reliability problems. Access points running LWAPP or 
autonomous IOS should transmit multicast and management frames at the lowest configured basic rate. 
Such behavior is necessary to provide good coverage at the cell’s edge, especially for unacknowledged 
multicast transmissions where multicast wireless transmissions may fail to be received.

Because multicast frames are not retransmitted at the MAC layer, clients at the edge of the cell may fail 
to receive them successfully. If reliable reception is a goal, then multicast frames should be transmitted 
at a low data rate. If support for high data rate multicast frames is required, then it may be useful to shrink 
the cell size and disable all lower data rates.