I have a strange problem with a Slackware 12.1 box of mine. It's set up as a router. It's worked fine now for a few months non-stop. There's 5 machines connected to this box on an internal network.

Today for some strange reason about 3 hours ago. This box will not let any internal machine connect to 3 websites that we've noticed. Not sure what has changed. It let you connected to most any site you want but these 3, and they just happened to be critical here, won't resolve.

If you're on the slackware machine it will open these sites.

I tried flushing the DNS on the machines that are on the internal network and I tried checking the iptables rules. Nothing seems out of the ordinary.

This tells me you should look at your provider I noticed this happened to me last week with At@T seems there was some firmware updates and had to do a complete restart of there modems which are also routers. It was strange it affected Yahoo google and a couple of my other sites. Please secure your IP modems because of a few internet bots are out there causing havic right now and if you have it left on default from factory and never set a password you are in trouble. Little info on the bot .
I had this complaint from a couple of people in my LUG and the ones I support. My personnel router has been hit by a bot a few times last week also the system did what it was supposed to do it filtered the sites the servers it was coming from. The causes some real slow down and failure of some sites till I did a cold reboot of the modem router. After the router is stopped the bot is killed the attack is over.
hope this helped.

I figured it out about 2 hours ago. I came here to post what I figured out.

I use 4.2.2.1 as my dns servers. That's what dhcpd serves up to my computers on the internal network. I noticed that eth0, the lan connected to my modem, is using the dns server from my ISP since nothing is defined in resolv.conf. So I figured I would change the dns server on one of my boxes to something else. That fixed the problem.

There is something up with the dns server at 4.2.2.1 not resolving those 3 domains for me. Probably more websites it wouldn't resolve that I didn't come across.

Probably just a temporary problem on their end.

Thanks for the reply.

yes when they did that they changed stuff. mark it solved and thank you for getting back.