Port forwarding does not work (using Merlin Firmware)

[Stefan1200]

I use an Asus RT-N66U router with a cable modem set in bridge mode. Asuswrt is showing my correct external IPv4 address. Currently using Merlin Firmware 374.41, but I had this problem also with 374.40.

After some tests with Bit Torrent (using port 5321) and FTP services I found out, that port forwarding don't work. Even if I disable my local firewall on my PC and the firewall on the Asus router I don't get a connection to my Windows 7 PC, ip: 192.168.1.240. PC is connected using LAN cable. Tried this with the connection tester of the Bit Torrent client and using a FTP client on my smartphone while using UMTS (not wlan). All tests failed, connection not possible.

What's the problem? Some ideas?

Here some information of the router protocols:

Connections (while downloading a torrent)

udp   81.162.56.98:6881              192.168.1.240:5321            UNREPLIED
udp   192.168.1.240:5321             37.113.185.122:6881           UNREPLIED
udp   192.168.1.240:5321             95.72.245.8:11888             UNREPLIED
udp   31.15.239.25:3940              192.168.1.240:5321            UNREPLIED
udp   192.168.1.240:5321             46.63.135.195:54550           UNREPLIED
udp   95.72.21.8:11888               192.168.1.240:5321            UNREPLIED
udp   192.168.1.240:5321             37.110.49.145:56881           UNREPLIED
udp   192.168.1.240:5321             86.100.222.204:10498          UNREPLIED
udp   192.168.1.240:5321             178.202.82.100:6241           UNREPLIED

Port Forwarding

Destination     Proto. Port range  Redirect to     Local port  Chain
ALL             TCP    5200:5399   192.168.1.240   5200:5399   VSERVER
ALL             UDP    5200:5399   192.168.1.240   5200:5399   VSERVER

Routing Table

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
31.16.215.254   *               255.255.255.255 UH    0      0        0 WAN
192.168.1.0     *               255.255.255.0   U     0      0        0 LAN
31.16.208.0     *               255.255.248.0   U     0      0        0 WAN
default         31.16.215.254   0.0.0.0         UG    0      0        0 WAN

 

[RMerlin]

Leave the router firewall enabled. Port forwards are actually firewall rules, so it won't work for sure if you disable the firewall.

If the forwards do show on the router's forward page, then everything is set correctly on the router's end. The issue would be with the client or the WAN side.

Most Torrent clients support uPNP, which is a much simpler way of handling the port forward, and also has the benefit of being able to use a randomly chosen port.

 

[Stefan1200]

Leave the router firewall enabled. Port forwards are actually firewall rules, so it won't work for sure if you disable the firewall.

Thanks for this information. While doing the most tests the firewall was activated.

If the forwards do show on the router's forward page, then everything is set correctly on the router's end. The issue would be with the client or the WAN side.

Ok, that sounds good.
I enabled the firewall logging, does the following two lines mean, that everything is forwarded to port 5321 correctly?

Apr 20 19:56:02 kernel: ACCEPT  <4>ACCEPT IN=eth0 OUT=br0 <1>SRC=183.178.105.107 DST=192.168.1.240 <1>LEN=296 TOS=0x00 PREC=0x00 TTL=112 ID=17702 PROTO=UDP <1>SPT=9429 DPT=5321 LEN=276 
Apr 20 19:56:05 kernel: ACCEPT  <4>ACCEPT IN=eth0 OUT=br0 <1>SRC=178.140.71.59 DST=192.168.1.240 <1>LEN=134 TOS=0x00 PREC=0x00 TTL=112 ID=30496 PROTO=UDP <1>SPT=52318 DPT=5321 LEN=114

Most Torrent clients support uPNP, which is a much simpler way of handling the port forward, and also has the benefit of being able to use a randomly chosen port.

For security reasons I don't like uPNP. And I also need the port forwarding for other stuff. Bit Torrent is just an example I used to test this, because the client has a nice port forwarding test.

Do you have an idea, what can do this kind of problems using Windows 7? I also disabled the Windows firewall.

 

[RMerlin]

Do you have an idea, what can do this kind of problems using Windows 7? I also disabled the Windows firewall.

I would double check that the client does use the specified UDP port. Also check your security software, some of them come with their own firewall which could potentially interfere.

 

[Stefan1200]

I would double check that the client does use the specified UDP port. Also check your security software, some of them come with their own firewall which could potentially interfere.

Now it works. It seems that the port forwarding tester of the Bit Torrent client has problems if uPNP is disabled. A HTTP server is reachable and works now.

Thanks for your help.