Symptom
For CAPWAP encapsulated client data traffic, packets may be lost, or throughput may be degraded.
Conditions
Seen with local mode APs (or FlexConnect centrally switched WLANs.)
TCP MSS adjust is not configured.
In some WAN or firewalled topologies, large or fragmented packets are discarded by the network, resulting in user data packets being lost over the CAPWAP tunnel (or EoIP tunnel, if anchored.)
Even with a path MTU of 1500 bytes between the AP and the WLC, the CAPWAP layer fragmentation will cause a
(usually minor) performance degradation.
Workaround
Simply configure TCP MSS Adjust (1250 recommended in most cases.)
From the AireOS CLI:
config ap tcp-mss-adjust enable all 1250
From the GUI: Wireless > Access Points > Global Configuration > TCP MSS => set "Global TCP Adjust MSS" to 1250
Further Problem Description
Resolution should be the value must be 1250 after upgrading to resolved code
1st scenario:when it is default value , after upgrade,it should show 1250
2nd scenario: when it is disabled in previous code and then upgraded to fix code, it should reflect 1250
