@EggheadCaptain 

The repeater may be getting confused as both the 2.4GHz and 5GHz are the same name. The repeater should work, but it will not work as a mesh-like the other Deco nodes.

@Tony My 3 Deco M9 Plus are in 3 spots of the house downstairs in straight line fashion, and they works fine for normal use.  Main router is in the middle.  However, performance in several bedrooms upstair is much worse than other area.  Kids' games are lagging and performance is poor.  Rather than ~200mbps downstairs, some area they play and study is only about 10 to 35mbps download.

My previous router ASUS 1900AC is not in use.  I have set up WDS in 2.4 and 5GHz, but not sure it is working as result is not always repeatable.  In fact, I am not sure if it is working at all, as the result sometimes is much better in one room but didn't improve in the other nearby room.  Both rooms are very close to Asus, so maybe better signal is only from Deco.

I have seen some instruction on your web site for router adding repeater but sure it if is applicable to Mesh like Deco.  It indicates additional configuration needed to be added to TP-Link router side.  

Can you provide some instruction on how to add my Asus as repeater to Deco?  Is there anything need to be done on Deco side?

Thanks

Tim

@EggheadCaptain 

No, you would not add the repeater from the Deco app, that would apply if it was Deco unit.

What you would do is set up the repeater and connect to the Deco wireless network. 

In order to reduce confusion, I would set up the repeater to have a different network name then the Deco. That way you know exactly what network you are connecting to.