More details are needed to understand the performance issues in mesh.
1- What controller is managing these APs?
2- What is the software version?
3- Distance between Root and Mesh AP.
4- Type of environment where APs are installed.
5- Third AP is connected to root AP directly or there are more than 1 mesh hops?
Please note that running a AP in mesh mode will give you half throughput than what you get from root APs. By adding additional hops, throughput will decrease by half from its last hop.
For example, refer below setup:
Wired network/SW >> Root AP >> Mesh AP1 >> Mesh AP2 >> Mesh AP3
In above Root AP >> Mesh AP1 (Throughput/2) >> Mesh AP2 Throughput/2 (Throughput/2)>> Mesh AP3 (Throughput/2).
So if I am getting 100M on Mesh AP1 then I will get 50M on Mesh AP2 and 25M on Mesh AP3.
It is not recommended to connect mesh APs beyond 2 hops because available throughput may not be enough to serve client requirements.
Syamantak Omer | Community moderator | Sr.Staff TSE | CWNA | CCNA | RASZA | RICXI