We are setting up an office with a Ubiquiti Unifi Security Gateway and three UAP-AC access points. The controller is running on a local Linux machine.
Most of the setup works fine. We are using a RADIUS server running on a Synology DS 2015xs for WPA2-Enterprise authentication. However, our clients cannot roam from one WAP to another. If a client is connected in one room and moves to another room it can take about five minutes until the client is assigned an IP address at the new location. In the meantime clients usually acquire self-assigned IP addresses and cannot connect to the internet or network. If the same client moves back to the first room, it will again take up to five minutes to regain a connection.
A client that stays within the same location can connect and acquire an IP address within a few seconds.
It is as if clients are "sticky" and remain associated with a particular AP for a long time. When a client is eventually released from that AP it can connect to a different AP but then will stay attached to that AP and will have to wait again before connecting to a different one.
I have ensured that the WPA2-Enterprise authentication is not the problem. All clients authenticate against the RADIUS server within a few seconds even if they need several minutes to acquire an IP address. I have also tested this with an open network and see the same problem.