RT-AC68u (A1) + Draytek Vigor130 3.8.4.1 = nat: apply redirect rules error!

[alistair]

Hello,

for about 4 years I used the combination of an RT-AC68u (A1 Revision) as my router, with the Draytek Vigor130 as the modem. This worked really well 99% of the time and I had no serious complaints. At some point Draytek released the firmware 3.8.4.1 for the Vigor130. My installed version was 3.8.4. As soon as 3.8.4.1 was installed (I always do factory default reset on the modem), I could no longer connect to the Internet. I had not changed any settings on the RT-AC68u. The firmware on the 68u was Merlin 384.19 - although I ended up testing different versions (down to 384.16), which didn't make any difference.

Checking the log showed, that the router now only displayed "nat: apply redirect rules error!" instead of connecting. This message was flooding the log. After I made sure all the setting were still correct in both devices, I installed the previous version 3.8.4 on the Draytek Vigor again. With the former firmware, I could immediately connect to the Internet again.

To this day I don't understand why my setup stops working, as soon as the latest firmware is installed on the Vigor130 modem. This version only has a minor fix, that shouldn't cause such a problem. I contacted the Draytek support and described the issue, asking if this was a known problem maybe and they said no. Since everything seemed to be working again with the older firmware, I stopped trying to find out what might be the cause here.

Recently I got the AX86u and installed Merlin 386.1. Having another router now, made me curious again if I would still get the same error as before - so I flashed 3.8.4.1 again on the Draytek modem but the exact same thing happened. Not knowing what the issue is, makes me really unhappy about using this modem. The AC68u and AX86u are very different routers, so what could this be? This latest Draytek firmware is generally incompatible somehow with the Asus firmware?

Has anyone else encountered this problem? Does anyone have an idea what the cause might be? Even if this can't be resolved, I still would like to know what the problem is.

Thanks!

 

[L&LD]

Did you test by turning off all your wired network infrastructure equipment for at least 20 minutes to an hour? After flashing the firmware you are testing on the modem?

Maybe, the connection needs to be reset between your modem and your ISP. With the new firmware, it may be possible that the ISP sees it as an 'additional' connection which it refuses.

 

[alistair]

I had everything turned off for up to 90 minutes. I watched a movie after pulling the plug on all devices and then continued. I'm quite sure this wasn't the problem.

 

[ColinTaylor]

I suspect that the firmware update changes the default IP subnet address so that it now clashes with that used by your LAN. What IP address range is your router's LAN configured for (e.g. 192.168.1.1/24)?

 

[alistair]

The Draytek Vigor130 is configured in pure modem/bridge mode. I also checked/compared the default config for the Draytek Vigor130 I'm using and there doesn't seem to be any difference in the web interface.

I also deleted/cleared the browser cache.

 

[ColinTaylor]

The only thing I can think of that would generate that NAT error message is a conflict in the IP address ranges. You could try changing your LAN subnet to something completely different (e.g. 192.168.90.1/24) to test that theory.