Strange DNS issues

[dscline]

First off, apologies for being a noob, I don't know if I have a firmware issue, a router issue, or a user issue (probably the latter). But I'm starting here...

Background: I just purchased an AC68w to replace an aging N16. The N16 was running a very old Tomato beta, mostly because I was just too lazy to upgrade it. But I never had any problems using it for the past 4-5 years, pretty much since they came out. When I got the AC68, I first upgraded to the newer Asus firmware due to some posts I read of some having issues getting the bootloader to update properly with the Merlin 378 betas. Then I went straight to 378.50 b2.

All seemed to go well, but I had one hitch: none of my PCs could browse the web. It seemed as if it was a DNS issue. I could ping IPs, but it seemed it would not resolve names. When I looked at the internet status page in the routers admin screen, it indicated the same Comcast DNS servers that were previously shown in my N16. I could ping those DNS servers from my PC. The "connect to DNS server automatically" setting in the router was set to yes, and I couldn't find many other applicable settings. I rebooted the router and modem, toggled the "Forward local domain queries to upstream DNS" to yes then back to no, nothing seemed to work, then all of a sudden, it seemed to fix itself. I don't know what the issue was, but just moved on since everything was working fine.

This morning we had a fairly major (~1hr) power outage. Both the router and modem are on a significant UPS, so they never lost power. But once the power came back up, the internet was again inaccessible. Strangely, email notices came in, but browsing didn't work. Any address I tried to browse to would go to the router's admin pages. I rebooted the router, then everything was fine again.

I know none of this makes any sense, at least it doesn't to me. But posting in case someone has an idea of what would cause this.

Thanks!

 

[AdvHomeServer]

here's a couple of ideas. They may or may not help.

1) Cable modems can be fussy when new routers are attached. Unplug it, wait a few seconds, and plug it back in. That might work,

2) Factory reset the router and let dhcp find your comcast account and set up your connection. Then minimistlcally configure the router for wireless. Don't fuss with any dns settings.

 

[RMerlin]

here's a couple of ideas. They may or may not help.

1) Cable modems can be fussy when new routers are attached. Unplug it, wait a few seconds, and plug it back in. That might work,

Make it at least 5-10 minutes, as the ISP must completely time out the previous session.

 

[RMerlin]

All seemed to go well, but I had one hitch: none of my PCs could browse the web. It seemed as if it was a DNS issue.

Check what DNS server is configured on your client. It should typically be set to automatic, which means they will be told to use your router's IP. The router will then do the name resolution using the ISP's nameservers, cache them locally, and hand the response to the requesting client.

Under Windows, use the following command to check your DNS servers:

ipconfig /all

 

[dscline]

Thanks for the replies. I'll have to do some more checking if/when some issues pop up again, but I don't think this was a cable modem issue. During the first issue, the router identified the correct Comcast DNS servers, and I could ping them. So it knew where to get the data, and seemed to have access to the data, but somehow didn't correctly pass that data on to the clients (and yes, I did check that the clients were using the correct DNS server... the router). The second issue was even more strange... for example, browsing to www.smallnetbuilder.com would show the router's admin page. I just can't explain that other than the router simply messing up the DNS responses. Every client on my network was being directed to the router's admin page regardless of the address searched, except I successfully got gmail email pop-ups (I assume because that IP address may have been cached on my PC?) . Doing nothing but rebooting the router fixed the issue.

It's all definitely very strange, I'll just wait and see if it happens again.