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Originally Posted by Redrobes What I expect is happening is that your router (which does the DHCP - dynamic host control protocol) is setting up your network DNS gateway addresses and it gets these from either a) somewhere other than your ISP or b) is fixed like say you set it up with OpenDNS. When you plugged into the ISP router you probably booted and fetched their DNS server addresses which were different. |
It is always best to use the DNS addresses that your ISP provides. The reason is that some DNS servers (most?) will refuse DNS requests from clients they don't recognize as a way of reducing their load. So if you're a client on one ISP's network and try to use the DNS servers of another ISP (or, potentially, even other DNS servers of the same ISP) your requests for DNS could be ignored.
If I were the network admin at an ISP, that's what I'd do.
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If you plug back into your router and find a site that you cant access then open up a command promp and type:
ping www.sitethatsdown.com |
If the problem he's having is DNS, then this will also produce a DNS error. The only way for him to know if it's a DNS problem (other than carefully reading the error message page the browser shows him!) would be to visit a site that allows you to type in a name and get their IP address, such as going to
http://netcraft.com/ and typing the domain name into the search box in the upper left. You'll eventually get a single page with their IP address. You can try putting that into your browser's Address bar and see what you get... (May not work if they're using name-based virtual hosting, which many sites use.)
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(replaceing site thats down.com for the yours- obviously...) and see if it tells you that its unreachable.
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Doesn't help much since many firewalls in front of web servers will block the ICMP "echo request" packet (commonly referred to as the ping packet).
I would suggest that the OP start by resetting his router back to Factory Defaults. That will clear any domain-based filtering done by the router. (I use such filters on my router to block ad-related sites like doubleclick.net and similar.)