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Suddenly can't connect to net

Posted on 2006-07-17
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Last Modified: 2010-04-18
All of a sudden, my small office network can't connect to the net through my Windows 2003 server.

3 Desktops
1 Server - AD, DNS, DHCP with static IP for server, File Server, Application Server (IIS), 1 NIC card
No routing services are installed on the server.
No firewall on the server. I am relying on NAT at the router

All machines are connected to the router.

Linksys Router - DHCP disabled
The Linksys router has no port forwarding or port filtering.

Either a cable modem or a DSL connection (we subscribe to both for redundancy)

This setup has worked flawlessly for 3 years until this morning.

Symptoms:

No machines can bring up web sites in the browser (e.g. Yahoo, Google, MS), download email or FTP, etc.
No machines can ping Yahoo, Google, etc.

All machines can see each other just fine including shared folders, drives, printers.
All machines can ping the router and browse its set up page in IE.
All machines can ping the gateway address of the ISP.
All machines can ping the DNS servers of the ISP.

On the server,

What I've done so far:
I have reviewed all DNS and DHCP settings and can't find any configuration issues.
I have substituted the cable modem for the DSL modem, renewed the IP address on the router.
Same issue with both connections.

I reset the router.
I swapped the router with another router known to be working.
No affect on issues.

When I eliminate the router and connect it directly to a desktop, the desktop is able to connect which is how I am posting this.
I am reluctant to expose the server, for a variety of reasons, and have not tested it.

I stopped and restarted DNS.
I did the same and rebooted the server.
No affect.

I stopped and restarted DHCP.
I did the same and rebooted the server.
No affect.

On the server, IE connection settings have no dialup connections and LAN settings option check boxes are all unchecked.

Network connections looks normal.

All I can figure is for some reason DNS is not looking beyond the server to resolve names.

Suggestions welcome.

Thanks in advance.


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Question by:bobinorlando
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SamuraiCrow earned 500 total points
ID: 17128223
A Couple of questions:

When you do a traceroute to www.google.com where does it break down? (Will tell you if it is a path problem)
When you do a NSLookup (on the client and server) against google.com can it resolve? (Will tell you if it is a DNS issue)
Is your ISP the only address listed on the DNS forwarder tab? (Verify correct DNS IP address with both service providers if necessary)
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by:bobinorlando
ID: 17129153
tracert yahoo.com
Unable to resolve target system name yahoo.com

nslookup can't resolve.

ISP dns servers listed in the forwarders tab "looked" correct to me since they're the same they've always been (just the name servers from Sprint our DSL provider.)
However, thanks to your prompting, I just doubled checked and the DSL DNS servers have changed.
Turns out the local phone company was sold off by Sprint and the new company has new DNS servers.
Makes sense, but I don't recall receiving any notice that a change was coming...

I have now changed the DSL name servers to their current IP addresses
and added the current cable company's DNS servers to the list.
Browsing is back.

tracert works as expected.
nslookup now resolves.

Problem solved!!

Thank you SamuraiCrow!
I accept your answer.
500 shiny points to you.

Best regards,

Bob

I have a related follow up question or two which I will be posting.


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