For blocking MU to MU within the same SSID, do you deployment details about VNS topology configuration?
- Is it configured as Bridge@AP
MU to MU traffic cannot limited if topology configuration is Bridge@AP.
Also Firmware V5.3.10 does not support filtering capabilities at AP, this feature was introduced at later point in release 6.1.
Looking at deployment hardware & firmware, it might be ideal to look into upgrade possibilities.