Server IP address cannot see Internet

Posted on 2005-04-12
Medium Priority
Last Modified: 2010-03-18

I have two servers that all of a sudden cannot communicate on the Internet.  I've tested the internal DNS by pinging computer names and other IP's of other servers and thats fine.

When you go to browse the internet IE just hangs and cannot find any addresses or IPs.  My default gateway is setup correctly, I can also ping it.  I've also flushed the ARP cache of the firewall\router.

Now the interesting thing is if I change the IP address of the servers having the problem, then it's goes out on the internet fine.  Once I change it back I have the same problem.  For obvious reasons I don't really want to have to change the server IP addresses.  

Why does this happen ?  How can I solve it ?
Question by:stevendunne

Expert Comment

ID: 13768290
Without knowing your current topology it appears that your DNS Forwarders aren't pointing to you ISP's DNS. Can you ping your ISP's DNS servers from your DNS servers?
LVL 13

Expert Comment

ID: 13768702
It sounds like an IP Conflict.   I cant think of another reason why your server would be gaining internet acceess by just changing the network address.

Do you have any errors in your event viewer?

Author Comment

ID: 13770730
I've tried disabling the NIC and enabling and then tried un-installing then re-installing.  The same problem persists.

From the server in question I'm able to resolve other computer names on the network and ping IPs of other machines.  I'm also able to ping the name of the problem server from another workstation and ping's it IP.  I've also checked the DNS forward & reverse lookup entries on both DC1 & DC2, these are fine, no duplicates, nothing strange.  And DHCP is clean as well.

So from this I'd assume DHCP & DNS are fine....

I've also flushed the ARP entry of this server from the firewall\router.  I've set another workstation to the IP in question and that machine doesn't work either, so it's the IP address thats doing it.  No IP conflicts messages, no event viewer messages.

Once I set the local area connection to DHCP, it's fine.  But I need to keep this server's current address.

How odd...........
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LVL 18

Expert Comment

ID: 13774654
Maybe the IP's in question are blocked by the gateway administrator, for some reason.

Author Comment

ID: 13780366
I resolved the problem by powering off the cisco router which is provided by our ISP.  I'd already called them to check our router was ok, and they said it was fine.  However it seems strange that it only affected 3 IP's from the LAN, and not any others, i.e workstations etc.  It was also interesting that these servers are published on the Internet with a public IP address.  However, 2 of my other servers which are on the Internet were not affected ??

Very strange.

Expert Comment

ID: 13780434
Great! Glad your systems are back up. If your router is using a distance vectoring method for discovery (RIP, IGRP, etc) it may have been caught in a contiguous loop with two or more adjacent routers at your ISP. Indeed, very strange.

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