AP6521 low speed after upgrade to wing 5.6

[Sungod]

I have three AP6521 (1 controller+ 2 adopted AP`s). After upgrade from Wing 5.4 to 5.6 wireless speed down to 80-100 mbps. Before upgrade speeds was 200-280 mbps. AP's works in 5Ghz mode. 

[Daren_Ellis · Accepted solution]

Hi Sungod,

I would highly recommend if "upgrading" AP6521 to try using the latest and greatest supported by that platform.
Recommendation:
5.8.6.13 or 5.9.1.10
 
After upgrade if speeds are still slow please confirm if all APs are using for 40Mhz wide 5Ghz channels.
Also post output from "show wireless radio st rf" and "show wireless client st rf"

Side Note:
This AP model has low memory so i would also recommend following article below for improved stability.
https://extreme-networks.my.site.com/ExtrArticleDetail?an=000074457