Hello, Freepix, I see your posts and i have the same model. So i sent the support a e-mail about this. They said that they will release a firmware to fix this in recent days. We can keep an eye on...

1. Check the security type, make sure it is not WPA/WPA2. For soho clients, you need select WPA/WPA2-Personal or WPA/WPA2-PSK. 2.If the TP-LINK is working as a repeater, make the security type...

TL-ER6120 can not support OSPF and other TP-LINK routers also can not.

How about try to use the latest firmware? It seems it has fixed some problems. http://www.tp-link.com/en/support/download/?model=TL-WDR4300&version=V1#tbl_j

I think the UN stands for "Universal", which means the firmware is suitable for the TL-WDR3600 product in most countries in the world.

The router says it is VPN passthrough. How about reboot the router? After you can log into the router, i think you can try to turn off the Hardware NAT to check the UDP can pass through or not.