Port Forwarding Intermittent UDP, Great TCP

[Kevin K]

Port forwarding seems to be intermittent for UDP but it works fine for TCP on my RT-N66U with Merlin 380.64.

My RT-N66U is in a LAN environment (i.e. My traffic is not passing to the Internet.) I have port 1194 set to forward both TCP and UDP to 192.168.8.10. At that address I have an OpenVPN server running.

If I connect my client directly to 192.168.8.10, the VPN works fine via TCP or UDP.

If I connect my client to the external address on my RT-N66U (192.168.1.64), the VPN works fine via TCP, but if I use UDP, sometimes it works and sometimes I get intermittent delivery of frames.

CPU utilization is low and I have lots of free RAM on my RT-N66U.

Any ideas on how to make UDP forwarding more consistent?

 

[Kevin K]

Interesting. If I connect to the external IP of my RT-N66U from inside the LAN, UDP is unreliable. If I connect to the external IP from outside the LAN, UDP is reliable. So out-and-back drops frames but from-out-to-in doesn't.

I suspect this to be caused by the VPN software and not the router.

 

[john9527]

What you are describing is NAT loopback, and there are two different implementations available. Try changing from Merlin to ASUS or vice versa.