What's the model and hardware version of the router you're using? As far as I know, TL-ER6120 V2/V3, TL-ER5120 V3/V4, TL-R600VPN V4 all support up to four WAN port. Since there are three WAN/ LAN...

Nope. Never heard of this kind of issue. Did you ever disable DHCP server or something? Suggested to reset your device and give it a try.

Never heard such kind of issue. You could post the virtual server configuration screenshot. I guess it was a setting issue. Maybe I can help.

KAYLUM wrote Just an update. I brought back my previous set up on my T470 since like what I said above, I haven't experience this problem before with previous router. The only thing I did is to...

tuanxuxu wrote I have been so and so far still can not handle, please help me What kind of VPN are you using? I found someone post this one and this fixes their PPTP VPN issue....

DO you know NAT table have aging time? From principles, I don't think NAT table and DDNS should correspond to Link Backup feature.