Sudden DNS issues with AC RT68U 386.7_2


Occasional Visitor
I am not savvy enough to explain the issue properly, but since about 2 or 3 weeks ago - intermittently my pc connected via Ethernet cable through router or my phone connected to a wi-fi on my routers network, would lose connection to the internet. When this happens if I click on the Ethernet button in Windows and check its status "it says IPv4 connectivity: no internet available". Then I could either switch it off and on myself, or use troubleshooter, which also switches it off and displays "The default gateway is not available" error. Meanwhile - router itself works, wi-fi works, Internet connection seems to be available, and I even accessed router from my phone to check it multiple times. Similarly, - wi-fi connection on my phone stops working and displays "err_name_not_resolved", while internet connection on pc is working perfectly fine.

If I connect to VPN or manually enter google or any other public DNS either in router settings or phone settings - internet connection starts working again. Which points to DNS issues on the router, or at least I think it is. It also doesn't seem to matter which DNS service I use, or if I just leave it on the ISP DNS - the issue happens anyway.

I don't have any specific settings or changed anything on the router page, and even removed some open ports I needed to check if the issue remains. I have tried reinstalling drivers, changing various settings, assigning default ip directly into tcp/ipv4 (resulted in no internet at all for some reason) but nothing has worked so far. The only thing I ever did to my router is updating its firmware and rarely opening specific ports, I did not change any other settings for years. I did not do a factory reset in a year or so, since I update firmware often, and readme usually mentions when it's necessary to do a factory reset.

What doesn't make sense and might be irrelevant info is that Ethernet connection/DNS on PC would drop after (but not before) 10PM, then maybe 1 or 2 times more in the next couple of hours, and never again after that, until the next day. While wi-fi/dns on my phone - just stopped working all together, unless I use public DNS either in phone, or router settings, or use VPN. On top of that - when it happens, even though router is definitely working, and internet is available, I am unable to open routers page from PC or my phone, depending on which one isn't working at the moment. After restarting ethernet adapter on PC or changing to public dns (or vpn) on a phone - router page opens again without issues.


Very Senior Member
Not sure what's going on there, but a reset might be a good try.

If you don't want to do a reset, though, here's a longer way:

1. Enable DNS logging for you.
Enable DNS logging method:
Enable custom scripts and configuration, then enter the following command:
echo "log-queries" >> /jffs/configs/dnsmasq.conf.add; service restart_dnsmasq

2. Look at the logs when the problem occurs.
When you think DNS failure happens, try using the nslookup command on the affected computer to resolve an arbitrary domain name and see what the router logs say.

3. Provides logs when the problem occurs for further troubleshooting.


Part of the Furniture
When you think DNS failure happens

A DNS failure would not cause a client disconnection. It would cause web sites not to load and time out. The clients will still stay connected to the router. The OP has another issue.


Occasional Visitor
Might have posted in a wrong subforum. Noticed there were other questions regarding that router here, but probably should've posted in lan and wan routers since this is a personal computer, and I don't run console.

I have been running continuing pings to my router and ISP, but so far never encountered that issue again. I'll try nslookup as well when it happens.

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