The same problem indeed. You should have read the explanation on #2 in that post, right? Well, it is a mechanism issue, not a bug... To ensure VPN passthrough work, after we enable Firewall, we...

Upgrade firmware of your C7 to be the latest version. Reset and reconfigure it. http://www.tp-link.com/en/download/Archer-C7_V2.html#Firmware

Firmwares of both WA860RE and C9 are up to date? Where did you "see" rate? If you place C9 next to WA860RE, what's the rate?

On WR841ND I set Network / WAN --> WAN Connection Type: Dynamic IP (before I had to have static + all values - because of service provider) If it works in WDS mode, WAN port is unplugged, isn't it?...

Any anti-virus software running on your PC? Did you try to login the web interface in local nework? What's the web browser? Try to clear browse cache. C2 is a brand new device? Power it off and back...

Hi Guys, Submit a ticket to report such a problem directly. http://ticket.tp-link.com/index.php?/Tickets/Submit