Product and Software: This article applies to all Aruba APs except AP-105/AP-9x
Aruba AP routinely sends jumbo frames to check if the MTU can be bigger than 1500. These jumbo frames are MTU discovery frames (SAPCP type 5). The payload is all 0s. If you do not force the MTU setting in the configuration, the AP will send out MTU discovery frames. This is expected behavior.
To stop this behavior, set the MTU size of the AP manually.