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Unable to connect to specific ip address -- but only from one location

Posted on 2004-10-13
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Last Modified: 2013-11-30
We have a new client (about a week) who has transfered their web hosting over to us. No problems at all the last week.

Today, about 15 minutes before closing time, we received a call that they were unable to connect to their admin area (receiving dns error in browser). We checked and all was well for us. Logged into one of their servers via terminal services and sure enough, could not connect to our webserver. Tried connecting to specific ip adresses was a no go as well. Able to connect to one ip address up and down so no problems there. Called the NOC and no problems there. Using Terminal Services, I connected to 5 other clients, spread out around the country and tried hitting the website in question and no problems there. Used AOL to receive new vpn and no problems there. Tried a few other vpn's and no problems there. Got to thinking maybe it was something up with time warner in their area (their isp). Called a couple of businesses in the area that are friends and that use TW and had them pull up the site in question -- no problems at all. So now we're down to it being their office...

Had them reset their modem -- but the girl didn't get the part about turning it back on and she went home. So tomorrow morning, I'll see if things are back to normal and if not, plan to do a /flushdns and poke around with nslookup. I'm thinking that's not going to fix anything though, as the problem is office wide, not just one specific machine.

Does anyone have any ideas as to what this could be? Is there something on the machine providing internet access to the rest of the office that could somehow be blocking a specific ip address and if so, where would I look? Any other ideas, no matter how trivial?

Mega thanks!
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Question by:1BC
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by:
vand earned 168 total points
ID: 12304615
First off, great job on your trouble shooting up to this point!

I would do some basic ping tests to ensure that the Name is being resolved correctly. If it is not you could do a DNS flush on the machine and check to make sure there are no manual entries in the hosts file.  If the IP is being resolved correctly you may want to look for software firewalls like zone alarm or XP SP2 which installs and activates a software firewall.

DNS seems to be the core issue. Are you able to connect via IP?
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by:wjc7662
wjc7662 earned 166 total points
ID: 12305283
My first thoughts point to a firewall, whether it's a software firewall or something in-line (maybe their router) I would need more topology information.
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by:brownmetals
brownmetals earned 166 total points
ID: 12322833
I’ve had a similar problem with not being able to resolve a domain name to an IP address after the IP address had changed. I have an in-house DNS server acting as a forwarder, using my ISP’s DNS servers. However, the DNS Host(A) record on my in-house server was pointing to the old IP Address of the domain. I’m not sure if your IP address had changed for this domain name in question, but I resolved the issue using the following steps:

1.      Opening the DNS console on the in-house DNS Server.
2.      Right click the DNS Server name > View > Advanced
3.      Open the Cached Lookups folder and drill down to the site in question. (Ex: www.brownmetals.com path would be ROOT> COM > BROWNMETALS)
4.      Look for the Host(A) record that is cached. If the IP address does not match the IP address of the corresponding domain name, delete the Host (A) record.
5.      Just to make sure, RIGHT CLICK the server name again, and choose “Clear Cache.”
6.      For each client, I used the /FLUSHDNS switch for the IPCONFG command.

Again, this resolution was used when the IP address for a particular domain name changed. Maybe some, or all of this solution will be relevant to helping solve your issue.

Good luck!
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