Radius protocol use the RFC 3580 from IEEE
https://tools.ietf.org/html/rfc3580
When a Station want to connect to the network need to made an Authentication Process with the AC which is the RADIUS CLIENT.
The AC comunicated through the APs to the Station and then to the RADIUS SERVER.
One option available to use as RADIUS SERVER is Windows Server 2012 or 2018
There is a known issue with the Size of the packet used by 801.x protocol.
Some stations have issues to procees a packet largen that 1500 octets and in case larger than 1000 octets.
In this sceneario the Station will fail to success the authentication process in result wont be available to connect to the network
Since the Station cannot process the packet, it will be discarded and won´t answer it lefting the AC waiting for the replay.
SOLUTION:
Change the MTU VALUE from RADIUS to a lower value, for example 800.
This will made the Packets be fragment in smaller packet of 800 bytes allowing the Stations to process this packet.
