Network Problem

[MacRS200]

I work in an serviced office where we access the main office network using remote desktop.

Our company has a number of IP addresses allocated on the service companies network that have internet access individually assigned as part of the service agreement. Consequently we use fixed IP and DNS addresses on each PC to access the local network and the net. Each PC has XP Pro as the OS, AVG anti virus with Windows Firewall enabled.

Anyway I shut down my PC as normal last night, got in this morning, fired it up and no internet access. Checked all the TCP/IP settings and they were all OK. Checked against the settings on the PC beside me to be sure and all were the same with the obvious exception of the IP address.

Tried switching off the firewall, reboot and still no joy.

Switched off AVG - nothing

Next I tried changing to the IP to the one from a PC that was switched off, no joy again.

Changed back to the IP I was allocated and went to the PC with the IP I had tried, fired it up and all was OK! So got on with some work.

Back to my PC later: -

Ran IPCONFIG and got the correct settings back IP, Gateway, DNS etc etc, this being the same as through control panel.

Ran NSLOOKUP and got

Can't find server name for address a.b.c.d: Timed out

Can't find server name for address w.x.y.z: Timed out

Default Server: UnKnown

Address: a.b.c.d

with a.b.c.d being the correct IP for the primary DNS server and w.x.y.z being the correct IP for the alternate DNS server.

Other PC's that work when I run NSLOOKUP give

Default Server: dns0.ispname.net

Address: a.b.c.d

Can ping IP addresses but not domain names

Ran TRACERT and I get IPs but no server names

I am at - must be a DNS problem on my PC as the same IP works on another PC. Looks like the unresolved Default Server name, if so how do I reset it or manually configure it either from command prompt or is there a registry setting I can change?

Is there anyone out there that can help it's driving me nuts.

Ta

Neil

p.s any posts from Tyger about Appfell will be ignored at best, at worst treated with total derision OK.

[Anees]

Hi Neil,

I'm sure you have already tried this, but the easiest thing to do would be to do a quick system restore back to maybe last week when it all worked fine?

Just so I understand this, you have individual external IP addresses for each PC; and each PC is directly connected to the Internet? Not using a router to share the same internet connection between many computers?

Try the system restore before we delve further :)

Anees

[Geoffers]

You're right, its a DNS issue.

It won't have a default server unless it receives a return from port 53 at a request. My first thought was the firewall blocking port 53 but you've tried it with it off.

I don't suspect any hosts file because its not showing any DNS names. Tracert won't show the names if it can't resolve at a server.

You need to see if is the DNS server rejecting you or the machine can't see any dns servers.

Try as Anees says but if no luck then try a free DNS server like 194.168.4.100 and 194.168.8.100 (NTL's are wide open to every ISP, well up until last week anyway. Confirm they are fine on your subnet by trying on another machine.). Or even set DNS to your gateway address as the odds are that will use dns forwarding unless switched off.

Change these in control panel or you can use netsh if you want from command line. While you are in the DNS settings of control panel, remove the default domain suffix while you are testing if there is one.

Drop to a command prompt and flush your dns cache first. (Ipconfig /flushdns)

Have you tried another PC on this IP? DNS may have been blocked on that IP or mis-allocated if someone has been programming the router at the provider end, but only for this IP. I've made this mistake if it is a higher end router. (I always get this wrong on the 2900 series, often pointing dns back to itself when setting up external services due to subnetting issues.)

If it is fine with the test DNS settings then you know the server is not responding to your requests. If it still doesn't work then you will know its definitely your PC blocking outgoing.

Could be the old XP winsock issue that rears its head every now and again, even with the latest versions. Its usually after a background clean up with an antivirus, adware or whatever but happens every now and again anyway. It gives the same issues as DNS problems. You can pick up the fix (which is really just a winsock reset) HERE

Double check AVG is shutting down properly too. Sometimes it doesn't completely disable and it could be blocking ports still. You may need to un-install and re-install. Use revouninstaller or something with a large database of programs to make sure it kills everything.

See how that goes if you haven't tried these already.

[MacRS200]

Hi Neil,

I'm sure you have already tried this, but the easiest thing to do would be to do a quick system restore back to maybe last week when it all worked fine?

Just so I understand this, you have individual external IP addresses for each PC; and each PC is directly connected to the Internet? Not using a router to share the same internet connection between many computers?

Try the system restore before we delve further :)

Anees

Hi Anees

IP is internal on a network and uses the same gateway on the network to access the net. Some IP's have net access and some don't according to the level assigned to the IP. The office has a big network and I assume uses a router to the gateway, only had a long range look at the server rack and it is the usual nest of patch leads about 3m long to interconnect over 2U

Don't know why I didn't think to restore

[Anees]

Don't know why I didn't think to restore

Hopefully the simple fix of the restore is all you need :D Otherwise Geoffers post give you a lot to try.

[Geoffers]

Ahh right - I though it was provider assigned public IP's forwarded to the PC's too.

[MacRS200]

Thanks chaps will give it a go again on Monday.

[MacRS200]

Thanks for the help guys, all sorted now :D

Tried my IP on another box and it all worked OK so not a problem with the IP or router.

Next did a system restore on mine and no joy. Next was switch to a new switch port through a different outlet on the wall still no joy.

Set the NTL free DNS on my PC and rebooted, as suggested by Geoffers, and off it went like a good'un. Switched back to the primary DNS that was originally set, reboot and hey ho back online. Changed back to my assigned outlet, ran NSLOOKUP and all was back to normal.

TBH don't really know what sorted it but it looks like the change of DNS gave it a kick and the change back sorted out the DNS cache.

Anyway thanks again.

Neil