Networking – Internet issues with subnet mask/DNS


I woke up today to find that my internet wasn't working. I checked all the cables, and everything was connected, I tried to connect to my router @ . It didn't connect. I checked the cables over again, I restarted the router, I restarted my computer, nothing was working. I ran ipconfig on the command line, and it said the subnet mask was I've never known what this is, but every time I've seen it, it's always been, so I opened up my network bridge and set it manually.

Voila! I was able to connect to my router. No internet access yet, but I could also connect to the modem. What was missing was the DNS servers. When I set the subnet mask manually, I had to set everything else manually too. I didn't know any off hand, but I had remembered that when I ran google's DNS benchmarking tool, its tertiary choice was the address of my router. I don't know what this means exactly, but I put it in and it worked.

How does having my router as a DNS server work? Is it using its cache, or is the router using the dns servers that would have been used if I left my computer on automatic? Also, why was my computer saying the subnet mask was Can I prevent this without setting everything manually?

I'm running Windows 7 Ultimate x86
I'm connected directly to an Actiontec ( router.
The Actiontec is connected to a Linksys (
The Linksys is connected to the TW Cable modem.

Best Answer

As Jim G said, a router typically forwards lookups to the IP of the DNS server it is configured for - To add... The benefit of this is that devices can register themselves in DNS so you can access via hostname - this would not work if you only used your ISP's DNS (excluding Netbios/similar).

As for the netmask... networking 101 time!

a netmask literally masks everything before it... For example, can be:


In the same way as: can be:

What I mean by this is, the subnet just defines what is on your own network, anything that isn't, requires you to go through the router. By using the range 192.168.1.x on a /24 ( subnet, simply means that anything from is on YOUR network, anything else has to go through the gateway.

By changing the subnet to a /16 or simply means that your network is -, but, as these are all private addresses, it really shouldn't make that much difference in a home network.

As to why it suddenly changed, and the fact you are using a bridge, all I can think is that it was either an update to the router/similar that caused problems, or a driver update on your machine.... but, it is an odd one.

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