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Constant DNS drops with Comcast (RT-N66U)

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kcharles520

New Around Here
Moved into a new house, Comcast is the only ISP option -- ever since moving in I've had constant, recurring DNS_PROBE_FINISHED-NXDOMAIN errors when browsing the internet. It happens anywhere from 2-5x a day and is highly frustrating.

The DNS drops off for all devices on the LAN simultaneously. At first I thought I needed to replace my router, so I swapped my Netgear out for the RT-N66U as it seemed highly reliable.

Nonetheless, the constant DNS errors remain. The RT-N66U has a really good log though, so perhaps someone can look at this and tell me what exactly is going on. This log is from right when the DNS dropped out at around 1:39PM today:

hu0h8i.jpg
hu0h8i.jpg


I suspect the issue is all on Comcast, perhaps a result of DNS hijacking or something. I've tried all sorts of things -- trying out a number of alternative DNS servers, changing the channel on my 2.4 ghz network, using static IPs on the LAN -- I just don't really know what to do at this stage.

If anyone can make sense of that log and offer some suggestions I'd appreciate it. Try to explain in layman's terms as I'm in no way an expert on this stuff :)
 
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Moved into a new house, Comcast is the only ISP option -- ever since moving in I've had constant, recurring DNS_PROBE_FINISHED-NXDOMAIN errors when browsing the internet. It happens anywhere from 2-5x a day and is highly frustrating.

The DNS drops off for all devices on the LAN simultaneously. At first I thought I needed to replace my router, so I swapped my Netgear out for the RT-N66U as it seemed highly reliable.

Nonetheless, the constant DNS errors remain. The RT-N66U has a really good log though, so perhaps someone can look at this and tell me what exactly is going on. This log is from right when the DNS dropped out at around 1:39PM today:

hu0h8i.jpg
hu0h8i.jpg


I suspect the issue is all on Comcast, perhaps a result of DNS hijacking or something. I've tried all sorts of things -- trying out a number of alternative DNS servers, changing the channel on my 2.4 ghz network, using static IPs on the LAN -- I just don't really know what to do at this stage.

If anyone can make sense of that log and offer some suggestions I'd appreciate it. Try to explain in layman's terms as I'm in no way an expert on this stuff :)

In layman's terms, the log says you need to call comcast to fix your internet.
 
In layman's terms, the log says you need to call comcast to fix your internet.

Lol, thanks.

I had them out last year -- they didn't do anything at all, just said the signal was strong and everything looked good on their end, but I kept having issues.
What exactly do I tell them needs to be fixed?

I doubt its the ethernet cable because I'm using the new one that just came with the router and I've also tried another cable as well....
 
Lol, thanks.

I had them out last year -- they didn't do anything at all, just said the signal was strong and everything looked good on their end, but I kept having issues.
What exactly do I tell them needs to be fixed?

I doubt its the ethernet cable because I'm using the new one that just came with the router and I've also tried another cable as well....

They can look at your modem logs and determine pretty quickly if the issue is on their end. Comcast has a forum that you can ask about your modem logs. It could be anything. Or you can post your modem log here if you want.
 
I have comcast and i can tell you first hand there customer service is the worse. They will blame the router for your problem so you should do some trouble shooting before you call them start here > http://forums.xfinity.com/t5/Basic-.../Connection-Troubleshooting-Tips/td-p/1253575 You can post your results here. If those levels that you can see from the modem look ok then you need to unhook the router and direct connect your computer straight to the modem and see if you still have disconnection issues if you do then make the dreaded call to comcast customer support.
 
Yeah it seems like Comcast comes out and as long as the signal looks good, they say "well it's your problem, not ours" which isn't fair. Another thing I did last year was bypass the splitter they were using to also connect to the TV, hoping it would solve the problem -- even that didn't seem to work.

And looking at the modem signal here, I mean, everything looks pretty good to me based on that link you provided:

1175s3b.jpg



As for plugging direct into the modem, I have done that a few times and the direct-connect to the modem is flawless -- I've actually never had a single drop when trying that and leaving it on for a whole day at a time. Once I go back to the wireless network though, its just constant disconnects.

That's why I figured maybe it *was* my router, but even with the upgrade to the ASUS, I'm still having issues. At this point I honestly have no idea how to make the wireless network more reliable, I've tried almost everything.
 
Yeah it seems like Comcast comes out and as long as the signal looks good, they say "well it's your problem, not ours" which isn't fair. Another thing I did last year was bypass the splitter they were using to also connect to the TV, hoping it would solve the problem -- even that didn't seem to work.

And looking at the modem signal here, I mean, everything looks pretty good to me based on that link you provided:

1175s3b.jpg



As for plugging direct into the modem, I have done that a few times and the direct-connect to the modem is flawless -- I've actually never had a single drop when trying that and leaving it on for a whole day at a time. Once I go back to the wireless network though, its just constant disconnects.

That's why I figured maybe it *was* my router, but even with the upgrade to the ASUS, I'm still having issues. At this point I honestly have no idea how to make the wireless network more reliable, I've tried almost everything.

It would make sense that your signal levels are fine most of the time. I guess I was talking about "logs" and not signal level. Your log will give you information such as sync problems...etc...

Example:

2015-05-24 16:12:15 3-Critical R007.0 Unicast Ranging Received Abort Response - Re- initializing MAC
2015-05-24 16:11:56 3-Critical D003.0 DHCP FAILED - Requested Info not supported.
2015-05-24 16:11:41 3-Critical R002.0 No Ranging Response received - T3 time-out (US 1)
2015-05-24 16:11:32 6-Notice M572.0 Rng Rsp Abort Status - Reinitialize MAC...
2015-05-24 16:11:32 3-Critical R007.0 Unicast Ranging Received Abort Response - Re- initializing MAC
 
It would make sense that your signal levels are fine most of the time. I guess I was talking about "logs" and not signal level. Your log will give you information such as sync problems...etc...

Example:

2015-05-24 16:12:15 3-Critical R007.0 Unicast Ranging Received Abort Response - Re- initializing MAC
2015-05-24 16:11:56 3-Critical D003.0 DHCP FAILED - Requested Info not supported.
2015-05-24 16:11:41 3-Critical R002.0 No Ranging Response received - T3 time-out (US 1)
2015-05-24 16:11:32 6-Notice M572.0 Rng Rsp Abort Status - Reinitialize MAC...
2015-05-24 16:11:32 3-Critical R007.0 Unicast Ranging Received Abort Response - Re- initializing MAC

I guess you could try updating the firmware to latest ASUS, or latest Merlin or latest fork.

After the firmware update, reset the asus router to defaults and reconfigure it from scratch.

What modem do you have? Or do you have a gateway?

Change the ASUS local LAN IP address to 192.168.22.1
 
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The modem is Motorola Surfboard. After looking at this log it *does* appear there were a few drop-offs with the modem itself -- which is odd, because I have direct connected to it in the past with no issues whatsoever. What the purpose of changing the LAN IP address? Just curious.

6qheef.png
 
Your signals are all good. After seeing your modem log you may have a issue those T-3 and T-4 timeouts are usually some kind of upstream issue. If you read that link posted above you will see there are two other levels that can not be read at the modem you would have to call and hope to get a rep that can give you those numbers. Do you notice the router issue coresponds to the rebooting of the modem ?
 
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Yeah I wonder if maybe there's something wrong with the outdoor wiring or something. I know the Comcast guy put a bunch of cable splices in the line when he installed it. I might have to get that checked out, could very well be the issue.
 

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