Computer on network has lost connection to network

[Furton]

Right, this problem has been driving me mad for the last few hours, so going to give you all the details.

First, network set up



All systems are running Windows XP Professional with SP2 and all updates installed with no other firewall installed except for SP2 firewall. All comps using AVG Free Edition

Situation

Last night was browsing the internet fine on my main computer and shuttle doing downloads as usual. Came back from work this afternoon and after booting up My main computer (shuttle is always on) it took a lot longer than usual to load the taskbar. Eventually it came on but the network icon was showing "Limited or no connectivity", noticed in IPConfig that no IP or DNS were set. Have tried the following things to repair the connection.

1. Tried the simple "Repair" connection, no luck
2. Put network cable into different network socket on on mobo (DFI UltraB), no joy
3. Put network cable into different port on switch, no joy
4. Replaced cable between Main comp and switch (and repeated step 2+3), no joy
5. Tried manually assigning IP and DNS, no joy
6. Checked router and DHCP table did not show main comp as being connected to network
7. Installed a PCI network card (tested on other machine and works), same problem
8. Un-installed drivers for on-board LAN, then re-installed, same problem.
9. Checked router logs, no sign of blocking my main comp
10. Disabled SP2 firewall, no joy
11. System restore to time when I know I was browsing the net, no joy.

I think I've done everything I can without re-installing WinXP (Which I don't really want to do), pretty much ruled out hardware problems as shuttle is downloading fine. Currently running a virus scan to eliminate that possibility.

Only thing I can think of is un-installing TCP/IP from the main comp, but that doesn't seem to be as simple on WinXP as on other versions of Windows (Would this work?, if so how).

Any suggestions or has someone come accross this before, I'm going nuts here.

[Paul Adams]

When you take the cable out of the main PC, does XP report "network cable unplugged"?

It doesn't sound like a problem with the clients, it sounds like you DHCP server in the router is FUBAR.
A reset may fix it, but bear in mind that any client which is currently working may well get kicked.

If you run "ipconfig /all" on the PCs which have a working network connection, when was the lease obtained, and when does the lease expire?
A DHCP lease should attempt to renew itself when it reaches 50% of the validity period.

If you set an IP address on the PC manually, and set the gateway & DNS servers to be the router, can you access the Internet okay from the main PC?
(Check the working PCs for an idea of a valid IP address, just change the last digit to 1 higher than the highest one assigned as a test.)

[Furton]

Yes, it does report network cable unplugged when disconnected

Have tried re-setting the router but all other network users seem to have no problems, even the shuttle on the same switch

This is what I get when ipconfig /all is performed on the shuttle comp

Windows IP Configuration

Host Name . . . . . . . . . . . . : shuttle
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Unknown
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : NVIDIA nForce Networking Controller
Physical Address. . . . . . . . . : 00-30-1B-AF-5D-8A
Dhcp Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.1.102
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1
DHCP Server . . . . . . . . . . . : 192.168.1.1
DNS Servers . . . . . . . . . . . : 194.72.6.51
194.72.6.52
Lease Obtained. . . . . . . . . . : 11 July 2005 19:42:19
Lease Expires . . . . . . . . . . : 12 July 2005 19:42:19

Nope, when setting IP and DNS manually the network icon in the taskbar stating "limited or no connectivity" disapears but still can't access the network/internet.

[Paul Adams]

With manually-specified IP settings, can you even ping the Shuttle or gateway from the main PC?
If you can't, type "arp -a" to list the resolution of all IPs to MAC addresses that the client managed to obtain.

Got any MAC filtering enabled on the switch?

Can you connect the PC directly into the router instead of the switch?

Did you change any duplex/speed settings in the network interface properties?
(For a switch I would assume Auto or 100/Full should be set.)

Did you change any MTU settings or anything on the client?

[Furton]

Right, your going to love this. Switched the cable from the router straight into My Main computer, internet/network works fine. hmmm

Plugged cable back into switch then switch to PC, same problem.

So two questions. Why would directly connecting the Router to the PC work instead of router -> switch -> PC, since the shuttle is going through the same set up.

Where is the actual problem then? Taking out the switch works (although not really practical as I need the shuttle for downloading over night), and the switch seems fine with the shuttle PC.

I'm just confused and hate computers even more.

[Paul Adams]

Originally Posted by Furton

So two questions. Why would directly connecting the Router to the PC work instead of router -> switch -> PC, since the shuttle is going through the same set up.

Where is the actual problem then? Taking out the switch works (although not really practical as I need the shuttle for downloading over night), and the switch seems fine with the shuttle PC.

All part of troubleshooting
If you take the Shuttle PC out of the switch and put the main PC into that port, does it work?
Does it work in any port on the switch if it is the only machine connected to it?

What you can do is get hold of Ethereal and WinPcap and capture network traffic on the main PC when it is connected to the switch, to see if it gets any response at all to the DHCP queries.
http://www.ethereal.com/distribution/win32/

Did you try the ping and ARP tests from before, when you assigned IP settings manually?
That should also show if you are able to get even layer 2 information correctly through the switch.

[Firelord]

May seem strange but have you power cycled the switch? If you powercycle for about 10mins (i.e. switched off for) just to clear down any static electricity and the ports and try again.

Does the switch have have an uplink/port switch? What make and model is the switch?