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Dougal

Bizarre Network Issue - I Need Your Help Please

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More a software issue than hardware I think, but here seems about the right place to post...

 

I have a main PC and several laptops on a wired network (or had). All running Windows7. Router is setup to retain static IP addresses also (for software reasons like SimConnect etc). Been using this setup for 2 years without problems, until now...

 

For whatever reason, I can no longer see the Main PC from one of the laptops, although I can still see and access the laptop from the others on the network. I know the workgroup is still okay as I've checked and double checked all the advanced settings, plus, I can still use 'Synergy' to control both machines with one keyboard and mouse, so the network itself IS functioning.

 

When I open the network on the laptop, it can only 'see' itself.

 

Driving me nuts that I can't solve this - any ideas please?


Windows 10 (x64) - X-Plane 11 - M/B: Asus ROG Maximus IX Hero - CPU: i7 7700k (@5.0GHz) - RAM: 32Gb Corsair Vengeance LPX DDR4 @ 3200MHz - Video: GTX1080ti - Cooling: Custom water loop (EK 140 Revo D5 pump/res combo, EK EVO CPU block, EK XE360 Rad)

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Hi Dougal;

 

Your laptops will have IP's like 192.168.2.2, 192.268.2.3, 192.268.2.4, 192.268.2.5, 192.268.2.6 192.268.2.7.

 

Your router port (the default gateway) for the above IP range should be 192.168.2.1

 

Go to that laptop, Dougal, and check it's Default Gateway. Do an "ipconfig /all" in a CMD window, and look for the 'Default Gateway'. It should be that router's port: i.e. 192.168.2.1

 

Second - if that's ok - in the same ipconfig /all window - check the subnet mask: this should be 255.255.255.0

Third - check that DHCP is not enabled - same window. - Actually as they're all laptops - just move one alongside the uncooperative one, and compare the two ipconfigs. You should see a difference between the two.

Come back and let us know the results.

 

All the Best,

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Hi Paul

 

Apart from the fact that my default gateway is always 192.168.1.254, and not as you stated, then all is as it should be. DHCP is not enabled and, apart from the actual IP addresses and mac addresses, all is the same.

 

Shame - I was hoping for a discrepancy;-)


Windows 10 (x64) - X-Plane 11 - M/B: Asus ROG Maximus IX Hero - CPU: i7 7700k (@5.0GHz) - RAM: 32Gb Corsair Vengeance LPX DDR4 @ 3200MHz - Video: GTX1080ti - Cooling: Custom water loop (EK 140 Revo D5 pump/res combo, EK EVO CPU block, EK XE360 Rad)

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Has your laptops wifi adapter picked up a DHCP address from another network? Maybe your laptop is trying to communicate via this in preference to the LAN connection which your other devices are using? Maybe temporarily disable Wifi to rule this out.

 

Could be a firewall issue on the laptop, try temporarily disabling it.

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DHCP is not enabled and, apart from the actual IP addresses and mac addresses, all is the same.

Shame - I was hoping for a discrepancy;-)

 

Yah - me too! I meant did DHCP somehow become enabled on that card? Stranger things have happened. PieEater has got a couple of good suggestions.. Did you take a look at the nic properties? Could be a duplex problem? You might check with one of the good ones and compare nic properties? There's lots of settings there.

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The gateway address doesn't matter so long as all the clients have the same one and it's on the same subnet.

You could try pinging the g/w and the other client PC, if it's the firewall it's likely to be blocking ICMP traffic. Use IPCONFIG and check the two devices. The subnet mask doesn't have to be the full Class C so long as you are within a valid range. in your config x.x.x.254 it will be simpler to ensure that the full Class C address range is the mask, so as above 255.255.255.0.

First step make sure that the two devices can see the g/w. Ping 192.168.1.254, that should return a response. If that works then try pinging each other, note that the gateway is irrelevant so long as the devices are on the same physical (or logical) LAN segment. If all of that works its going to be at the upper OSI layers, so something with either the software you are using or the firewall on either machine.

If you are unable to ping either machine or the gateway, it could well be the windows firewall, generally it won't stop outgoing pings but will stop incoming packets that are intiated from another source (echo-response is a separate port) Your g/w will hopefully be configured to accept any traffic from the LAN side and so should respond. NIC issues are unlikely, they tend to operation in full duplex as default, unless something has been in and played with the settings.


Ian R Tyldesley

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This really is strange - i've never seen anything even remotely like this happen.

 

All machines on the network have Windows Firewall completely disabled, along with UAC.

 

All machines can also ping each other AND the router, and yet, this one laptop cannot see any other Public folders or machines:-(


Windows 10 (x64) - X-Plane 11 - M/B: Asus ROG Maximus IX Hero - CPU: i7 7700k (@5.0GHz) - RAM: 32Gb Corsair Vengeance LPX DDR4 @ 3200MHz - Video: GTX1080ti - Cooling: Custom water loop (EK 140 Revo D5 pump/res combo, EK EVO CPU block, EK XE360 Rad)

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How about THIS for even more bizarre then....?

 

If I enter \\192.168.1.79 into a windows search bar of the laptop, it brings up all my shared folders on the main FSX PC.

 

So why on earth then do you suppose they dont show up in the Windows Network list?

 

Crazy!


Windows 10 (x64) - X-Plane 11 - M/B: Asus ROG Maximus IX Hero - CPU: i7 7700k (@5.0GHz) - RAM: 32Gb Corsair Vengeance LPX DDR4 @ 3200MHz - Video: GTX1080ti - Cooling: Custom water loop (EK 140 Revo D5 pump/res combo, EK EVO CPU block, EK XE360 Rad)

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All machines can also ping each other AND the router, and yet, this one laptop cannot see any other Public folders or machines:-(

 

Forgetting the "Windows Network" discovering other machines for a moment, Dougal - sitting at the bad laptop - can you map a drive (which exists) on another latop? (Windows Explore->Tools->Map network drive)

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If your laptop cannot resolve IP addresses to names then this would suggest a DNS issue, are you sure that you have correctly specified the DNS server entry in your IP configuration? You could try flushing the local DNS cache - ipconfig /flushdns (requires elevated command prompt) and checking your DNS client service is running (services.msc).

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All machines can also ping each other AND the router, and yet, this one laptop cannot see any other Public folders or machines:-(

 

This statement is rather contradictory, how can "All" machines ping each other, yet the laptop (one presumes a machine) cannot see other machines? Do you mean that the laptop can ping but not access other services?

 

If it's a DNS problem try nslookup from a cmd prompt. It should return a server address, if you type google.com into it, the name should change into a ip address. Unlikely your local machines will work, you tend to need static lmhosts / hosts entries for these, depending on the machine type anyway.

 

Back to the laptop, if you are able to ping can you tracert from the laptop to the machine in question? Depending on the device you should see only one hop (the machine in question).

 

Any protection on the router / switch ports the devices are plugged into? Wireless network isolation? Mac Filtering? What does the ARP cache say (arp -a...in cmd) can you see the hardware devices of the other machines? Does it have a timeout or does it say something like incomplete?


Ian R Tyldesley

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Hi guys and thanks a million for all the suggestions. I've made a decision to reinstall windows on the laptop as there is also some other issues.


Windows 10 (x64) - X-Plane 11 - M/B: Asus ROG Maximus IX Hero - CPU: i7 7700k (@5.0GHz) - RAM: 32Gb Corsair Vengeance LPX DDR4 @ 3200MHz - Video: GTX1080ti - Cooling: Custom water loop (EK 140 Revo D5 pump/res combo, EK EVO CPU block, EK XE360 Rad)

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