@PraveenC Check this answer and the A9 FW page. There's no OneMesh support for A9. What you've posted is probably a slide that hasn't been updated by the site administrator.

@Rnd.dipa Try these wireless settings:

@Suhailmyself If you have a Range Extender mode in your Archer C20 you won't have WDS option - it's either one or the other (except in TL-WR940N). In newer router models WDS has been replaced by...

@vasik006 If setting the SSIDs on C6 different than these on the main router makes re-connection smoother keep them that way - you're not gaining anything if you set them identical. If you're not...

@Pro4TLZZ Check this story - for details on available channels on the 5 GHz band using 160Mhz channel width.

@alexino Set these from here: