RT-N66U and DDNS Quit Working?

[mike7143]

Looking for some help on a DDNS issue that's suddenly started. RT-N66U on 380.65_4.
DDNS is with FreeDNS and my domain has been working fine for years; I've got my ddns-start script set up, it's been working fine for over 2 years when I bought this RT-N66U. Few days ago I lost access via my domain, thought maybe internet was out; nope, TeamViewer still connected. Rebooted some stuff, no luck. Checked FreeDNS to see what IP it had, it's correct. Checked various DNS propagation sites, they're all seeing the correct IP to domain as well. Don't know what to do or where to start. Seems to be the router itself I think because using the direct IP and my access is works, my script hasn't changed (re-verified it), FreeDNS is up to date, and it's propagated...

Any ideas? Don't really want to reset anything as I have tons of settings I'm not keen on trying to re-do. Then again, I think my software is way out-of-date and maybe I need to update?

Thanks!

 

[mike7143]

My ISP assigned a new WAN IP today, the ddns-start script did its thing and FreeDNS updated as expected and is propagated. Unfortunately I still can't use the DNS. It's like everything is working as it should, updates work, but like the router is rejecting incoming connections somehow? If that's even possible. But replace the addresses/urls with the WAN IP and it works. Any ideas?

 

[RMerlin]

Your problem has nothing to do with DDNS. If it gets updated, then your issue is with the application itself or a firewall blocking it.

 

[mike7143]

It's not one specific application; my IP webcams don't work, remote desktop doesn't work, FTP doesn't work, etc. But if I change from the DNS name to the IP, they all work?

 

[mike7143]

I've been through every settings page in the GUI, I can't find anything that appears to be setting to block all external connections by only the host address but not the IP address directly. The DDNS service appears to be working still, it's being propagated, but I still can't use my host name for connections... any other ideas? I didn't change anything in my router, it just quit working one day when I noticed I couldn't access IP cams.

 

[mike7143]

I just had a thought... is there any way this could be something my ISP is blocking or has changed recently without me knowing? I'm not aware of any setting in the modem's GUI that I'd change this, is a SB6121; I don't think there's really anything I CAN change on the modem...

 

[mike7143]

Still can't figure this out and it's driving me nuts having to manually update IPs...
Over the weekend I did a complete factory reset of my router's firmware. Then I updated the firmware (from 380.65_4 to the latest LTS from john) and put my ddns-start script back.
Script works, it updates the IP in FreeDNS, but I still can't access remotely with the DDNS with any application/software.
As previously mentioned, it was working fine on 380.65_4 for years then suddenly stopped working one day, no changes made to the router.
Any ideas?

 

[dave14305]

Give a specific example of an access attempt that doesn’t work. Are we talking about router GUI access over the WAN (bad idea)?

Even if nothing works, it’s best to start troubleshooting a single use case.

 

[ColinTaylor]

So to be clear.....

From an external client you can do an nslookup on your DDNS name and it returns your router's WAN IP address. Correct?

If you then try to access your router using the DDNS name it fails, but if you use the IP address it works. Correct?

 

[mike7143]

Give a specific example of an access attempt that doesn’t work. Are we talking about router GUI access over the WAN (bad idea)?
Even if nothing works, it’s best to start troubleshooting a single use case.

I have an IP webcam that's wired to the router. It's got a static IP address and a port number configured in the IP cam. In the router I have port forwarding set up so that connections to that port number go to the IP cam's IP local IP address. Using an Android app to view the camera remotely, I used to have the address entered as my.ddnsname.com and my specific port. And I could be on my mobile 4G connection and view the IP camera.

Now, with the same setup, I get the app reporting an error saying host unreachable. But if I go into the app and change it from my.ddnsname.com to my current IP address, it works.

Another example. Had a Windows 7 machine with a static IP address on my local network. I went into regedit and changed the default port number for Windows RDP from 3389 to a different port. In the router, I had forwarded that port to my machine's local static IP address.

From a machine at work, I could remote into it using my.ddnsname.com: port number and it'd connect. Now, it won't connect, RDP errors out. Change it to public IP address as x.x.x.x: port, I can connect.

Don't worry, I don't have RDP exposed anymore.

 

[mike7143]

So to be clear.....
From an external client you can do an nslookup on your DDNS name and it returns your router's WAN IP address. Correct?
If you then try to access your router using the DDNS name it fails, but if you use the IP address it works. Correct?

Yes. If I use any of the multiple DNS lookup tools online (remotely), it shows the IP as correct but when I try and use it, it doesn't work. Replace DDNS with the actual IP, connection works. Was working properly for years, then one day it quit working; no changes made to the router.

Almost wondering if my ISP is somehow blocking something...

 

[ColinTaylor]

Sorry, I can't think of any rational reason for this behaviour.

Almost wondering if my ISP is somehow blocking something...

That was my initial thought, but that makes no sense. The DDNS name is resolved into an IP address before it leaves your client. There might have been a possible issue there if connecting to a web server but you say you're having the same problem with RDP - a completely different protocol on a completely different port.

 

[L&LD]

Still can't figure this out and it's driving me nuts having to manually update IPs...
Over the weekend I did a complete factory reset of my router's firmware. Then I updated the firmware (from 380.65_4 to the latest LTS from john) and put my ddns-start script back.
Script works, it updates the IP in FreeDNS, but I still can't access remotely with the DDNS with any application/software.
As previously mentioned, it was working fine on 380.65_4 for years then suddenly stopped working one day, no changes made to the router.
Any ideas?

You did this in the wrong order.

First, you need to flash the firmware you want to use.

Then, you perform a full M&M Config (reset to factory defaults and then a minimal and manual configuration of the router to secure it and connect to your ISP).

Please see my signature below for links and further details on getting your router to a good/known state.

Afterward, if any issues still seem to be present, others will be better able to give you usable suggestions to fix them.

 

[mike7143]

Sorry, I can't think of any rational reason for this behaviour.

Well shoot, the way you'd posed the question so direct, I thought for sure you'd be ready to whip out an exact reason! But hey, thanks either way!
I suspect I'd have to spend about 5 hours on the phone with the ISP just to get to a real person who actually knows what I'm talking about, just to find out if they're messing with something, and if they'd even admit it if they were...

If nobody else is having this issue, and it was occuring on 380.65_4 as well as after I changed to john's LTS.... maybe I'm in the wrong forums... or I'm nuts!

 

[mike7143]

You did this in the wrong order.

Well, I don't disagree... Didn't know that was the correct way! And not saying it can't be my issue; but how's that line up with DDNS working for years, no changes, suddenly breaks?

Appreciate the info though and M&M, I would have never have guessed to do that!

 

[L&LD]

Well, I don't disagree... Didn't know that was the correct way! And not saying it can't be my issue; but how's that line up with DDNS working for years, no changes, suddenly breaks?

Appreciate the info though and M&M, I would have never have guessed to do that!

When you updated the firmware to john9527's LTS fork, the router's old variables, and other microcode and miscellaneous bits and pieces were still using (or trying to use) these bits with the new firmware you flashed. Things can go south here really fast when this situation happens.

By flashing the firmware you want (LTS fork) first and then doing a full reset to factory defaults, you are ensuring that the new firmware will have the best chance to work the way it was designed.

Looking toward your return with your router in a good/known state.

https://www.snbforums.com/threads/f...lts-releases-v38e4.18914/page-459#post-477105

The above post lists some additional steps you may want to try (and I suggest you do) to make sure this works on try 'one' for you.

 

[dave14305]

Is there any difference in the IP that your router thinks is its WAN IP and the IP reported by www.whatismyipaddress.com? Just wondering if your isp is hiding your real IP somehow. Grasping here...

 

[mike7143]

Is there any difference in the IP that your router thinks is its WAN IP and the IP reported by www.whatismyipaddress.com? Just wondering if your isp is hiding your real IP somehow. Grasping here...

Nope, router's reported WAN and what's shown on that site are the same IP address!

 

[dave14305]

What about the output of these iptables commands?

iptables -t raw -S
iptables -t filter -S

Nevermind. It wouldn't make sense since it all works via IP address. And is the IP being resolved externally for your DDNS name the same as the IP you saw earlier in router and website? Any IPv6 in your network?

 

[mike7143]

Nevermind. It wouldn't make sense since it all works via IP address. And is the IP being resolved externally for your DDNS name the same as the IP you saw earlier in router and website? Any IPv6 in your network?

Yes. IP is properly resolving correctly. No IPv6 either.