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DNS Lookup Failure... With A Twist

Last response: in Networking
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October 1, 2012 7:36:21 AM

Hey all,

Yesterday we (family and I) installed a new modem in our home. a "Motorola DOCSIS 3.0 modem". We hooked it up and registered it with our ISP. Upon installing it every computer/device on the network (both wired and wireless) worked, except mine. Only Skype was connected to the internet and working fine, while every other browser/application would give me "DNS Lookup Failure" errors.

From here I just did the old "unplug and pray" and unplugged everything (Router + modem), waited 10 seconds, and re-plugged everything back in. That seemed to work... but only for 4 hours.

4 hours later my computer just instantly disconnects from everything (battle.net, spotify, etc) EXCEPT Skype.

The router we use is the "Sonicwall TZ-105".

Things I've tried so far to solve the issue:
Manually input IP address
manually input DNS servers (both my ISP's and Google's 8.8.8.8 etc)
Unplug/re-plug modem and router
used different port on router
plug computer directly into modem

all of these things ^ haven't worked :(  I tried calling my ISP today, and they said that I had to buy their "premium tech support package" which costs $99.99 for a tech person to come out, and $15 monthly just for the service... Which was way overpriced, and I don't want to wait a week for someone to come out and try to fix my internet.

Also, talking to the Router service currently but they are extreeeeemely slow when it comes to responding back to "cases". Calling them has been very unreliable in the past.

They most recently told me to "Check for any outbound NAT policies related to this computer i.e. created using the IP of this computer." However, they never even told me HOW to do it.


Any Ideas? :p  Right now my computer is just a glorified skype machine, while all the other computers on the network are running better than ever
October 1, 2012 12:46:14 PM

Since it is only a single machine I would be suspect of firewall setting or the virus software. Try to temporarily disable them.

Make sure you can ping the dns servers from a cmd window. You can also try to telnet into dns server on port 53. It won't really connect but it looks different than if you were to telnet into a blocked port.
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October 1, 2012 3:09:25 PM

Odd, where did you get the sonicwall? Was it given to you by your ISP? Sonicwall's are generally business routers and have a lot more complexity when it comes to setup than a normal SOHO router. Also, without a sonicwall support contract, help will be minimal.

If you aren't familiar with setting up firewall rules , NAT rules, and ACL's, I'd suggest you purchase a more suitable router.
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October 1, 2012 5:33:11 PM

bill001g said:
Since it is only a single machine I would be suspect of firewall setting or the virus software. Try to temporarily disable them.

Make sure you can ping the dns servers from a cmd window. You can also try to telnet into dns server on port 53. It won't really connect but it looks different than if you were to telnet into a blocked port.


I have already uninstalled all antivirus software and disabled the firewall :p  Whenever I ping DNS servers I just get "Request Timed Out" 4 consecutive times and then it stops.


Hawkeye22 said:
Odd, where did you get the sonicwall? Was it given to you by your ISP? Sonicwall's are generally business routers and have a lot more complexity when it comes to setup than a normal SOHO router. Also, without a sonicwall support contract, help will be minimal.

If you aren't familiar with setting up firewall rules , NAT rules, and ACL's, I'd suggest you purchase a more suitable router.



Trust me I know the complexities of this router. My father just asked someone what the biggest and best (and most expensive) router is and purchased it... However I know very well that this router is not suited for home usage. We needed a freelance tech guy to come out and set it up for us, and, after consulting him about my issue he suggested that I reformat my computer.

However I don't really want to do that because 1. If it still cannot connect, then I just have an even more worthless computer and wasted all that time.. And 2. I don't think it's the computer that is the issue. If the computer wasn't connected to skype and didn't say it was connected to the internet then I would believe that it was the computer, however I feel it is the router
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October 1, 2012 6:02:47 PM

Has me concerned that you said it does this when you plug directly into the modem, that would imply it is not the router.

This is also the symptom if someone is trying to block access using opendns. There are also a number of trojans/virus that have this symptom.

What happens if you put some of the location in the etc/HOSTS file.
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October 1, 2012 6:52:50 PM

shew said:

Trust me I know the complexities of this router. My father just asked someone what the biggest and best (and most expensive) router is and purchased it... However I know very well that this router is not suited for home usage. We needed a freelance tech guy to come out and set it up for us, and, after consulting him about my issue he suggested that I reformat my computer.


Sorry for going off topic. Without a sonicwall support contract, I don't even think you can upgrade the firmware on a sonicwall. The TZ is an older model. If it hasn't had a firmware update in a while, it's probably got security holes and left over bugs. if you plan on keeping this router I suggest getting a minimal support plan that offers software updates, otherwise I recommend you switch to a modem more suited to home users.

Just to keep on topic... bill001g has a point. If you continue to have DNS probelms when simply attached to the modem, then this eliminates the router as a problem.
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October 1, 2012 7:51:21 PM

Hawkeye22 said:
Sorry for going off topic. Without a sonicwall support contract, I don't even think you can upgrade the firmware on a sonicwall. The TZ is an older model. If it hasn't had a firmware update in a while, it's probably got security holes and left over bugs. if you plan on keeping this router I suggest getting a minimal support plan that offers software updates, otherwise I recommend you switch to a modem more suited to home users.

Just to keep on topic... bill001g has a point. If you continue to have DNS probelms when simply attached to the modem, then this eliminates the router as a problem.



Pretty sure we have a support contract because I updated the firmware on the day that we got our modem. Unfortunately, I don't remember if I updated the router before or after my computer "failed" for the second time.

I tried plugging directly into the modem and it wouldn't work. I tried setting up a new connection etc on windows 7, put in our account name + info for ISP, but i could not connect to the internet. I may be just using the direct connection to the modem incorrectly, not sure exactly how to do it
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October 1, 2012 7:56:54 PM

There's not much too it. Plug the ethernet from the modem directly into your computer. This should be the cable currently going from your modem to the WAN port on the sonicwall. Make sure your computer's TCP/IP settings are set to "automatically obtain an IP address" and "automatically obtain DNS". That should be it.
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October 1, 2012 9:09:14 PM

Hawkeye22 said:
There's not much too it. Plug the ethernet from the modem directly into your computer. This should be the cable currently going from your modem to the WAN port on the sonicwall. Make sure your computer's TCP/IP settings are set to "automatically obtain an IP address" and "automatically obtain DNS". That should be it.



Tried this, when I plug it in it trries to find the network for a while then has like "unrecognized network" and cannot connect to internet. I try to set one up and it only lets me set up broadband, and any username/password I use will not let me connect.

This happened on our old modem before, for some reason I cannot connect directly to the modem itself
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October 1, 2012 9:15:34 PM

Always power cycle the modem after connecting a new device to it. Modems grab onto the first MAC address they see at initialization and will not talk to any other NIC until reset.
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October 2, 2012 12:24:20 AM

ex_bubblehead said:
Always power cycle the modem after connecting a new device to it. Modems grab onto the first MAC address they see at initialization and will not talk to any other NIC until reset.


Did this, and it works ^.^ So that pretty much guarantees that it is the router causing the issue?
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October 2, 2012 12:25:30 PM

You said your connection drops like every 4 hours. Did you leave your computer directly attached to the modem for 4 hours or more to see if it disconnects? If it doesn't, drop then being that your are the only one in the house that gets dropped makes me think it's a router configuration setting. Since you said you tried other ports on the router, it's not a port specific setting. It alsmost sounds like an ACL tracking your MAC address or something. I think your going to need the tech that set up your router to come back and look at the firewall rules, NAT policies, and any ACL's or purchase a simpler router. A sonicwall is definately overkill for the typical home user.
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