Windows - internet not working on specific IP

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I have a weird problem with one workstation. It's a computer running Win10 Pro with a static IP configuration. The IP was set more than year ago and it was working fine. Until today, when it suddenly stopped working. I thought it's a problem with firewall or NIC, but after few hours of troubleshooting, I came to this:

  • When the IP is set to 192.168.5.107, all outgoing connections timeouts
  • Once I set it to 192.168.5.108, everything is working fine
  • When I set it back to 192.168.5.107, I'm back to timeouts
  • Setting it again to anything different than 192.168.5.107, it works again
  • In some cases, I was able to RDP to the computer on 192.168.5.107, but it was working kinda randomly

I double checked that no device in my network is using 192.168.5.107 and that this IP is out of DHCP server range.

Screenshot of IPv4 settings that worked for last year

Do you have any suggestions what could be causing this problem? I could change it to working IP, but I want to know why is this happening.

//EDIT: I tried setting the IPv4 settings from the screenshot on 4 different workstations in the network and it's working fine. Also, to make sure there is no IP collision, I unplugged all devices from the network, leaving only the router (192.168.5.1), this workstation (192.168.5.107) and my laptop (192.168.5.152). Still as soon as I set this workstation to 192.168.5.107, all outgoing ping requests timeouts. If I set it to anything different, internet works fine.

192.168.1.1 is main gateway for the whole network. See the network diagram.

Adam Ježek

Posted 2017-12-18T23:15:17.613

Reputation: 51

1sounds like another device is using that same IP - some devices reject scanning attempts so it won't turn up on any network scans. Just use dhcp or set a known good address – JohnnyVegas – 2017-12-18T23:23:36.197

@JohnnyVegas Impossible. I even disconected all devices (Wi-Fi AP's, other computers, printers, etc) so ONLY THIS ONE workstation was connected to the router. Also, ping to 192.168.5.107 returns "destination host unreachable" – Adam Ježek – 2017-12-18T23:25:57.077

not being able to ping isn't proof. some devices reject ping scans. Install nmap and type nmap -v -A 192.168.5.107 -Pn - that may find the device but it isnt guaranteed. – JohnnyVegas – 2017-12-18T23:27:55.387

also, the first DNS address is completely wrong. Set to 192.168.5.1 or 8.8.8.8 or change subnet from 255.255.255.0 to 255.255.0.0 – JohnnyVegas – 2017-12-18T23:29:52.930

@JohnnyVegas 192.168.1.1 is gateway provided by ISP, 192.168.5.1 is router for this subnet. 192.168.1.1 is pingable from and used as DNS by all computers in this subnet for few years. Also, using the configuration from screenshot works on any other PC in network, there must be some dark magic happening on this workstation. – Adam Ježek – 2017-12-18T23:40:00.923

You have used the subnet 255.255.255.0 so the 'dark magic' is you are not using the right subnet. 192.168.1.1 cannot be accessed by 192.168.5.1 as you are not using subnets correctly. – JohnnyVegas – 2017-12-18T23:44:10.770

@JohnnyVegas Than how do you explain this? https://ctrlv.cz/shots/2017/12/19/sp4J.png Please note that 192.168.5.1's WAN port is connected to 192.168.1.1 LAN port. 192.168.1.1 is main gateway and other subnets are in cascade-style network

– Adam Ježek – 2017-12-18T23:47:41.933

192.168.5.1 has the correct subnet and resolves 192.168.1.1 as it should. – JohnnyVegas – 2017-12-18T23:54:40.647

@JohnnyVegas I edited the question to make it more clear and added a network diagram. This configuration was workign for the last year and I made NO CHANGES to the network. It f*cked up after Windows update. Also, the problem is not only that the PC can't access 192.168.1.1. It can't acces ANY IP. 8.8.8.8, 192.168.5.1, nothing. As soons as I set the IP to 192.168.5.107 on this PC, all requests timeouts. Setting this IP on any different PC in this subnet works fine, – Adam Ježek – 2017-12-19T00:05:43.540

1Is there a switch between the workstation and router? It kind of sounds like a stuck ARP entry in a switch. What if you setup a different device like a laptop with 192.168.5.107 and connect it to a different port directly on the router and disconnect the workstation does that work? – acejavelin – 2017-12-19T00:19:37.523

@acejavelin Yes, there is a switch, and if I use the IP config from screenshot on another PC in this switch, it works. I also tried replacing the switch with one from different manufacturer (I don't have the same one) and the problem persists, so I believe that Windows update just made some dark magin on this workstation. Also tried removing the switch and connecting directly to the router, results are the same. – Adam Ježek – 2017-12-19T00:26:15.490

netsh int ip reset then reboot – Hicsy – 2017-12-19T01:29:28.887

Answers

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The most likely cause of that issue is a duplicate IP on the network. If you're using a typical home router device (that does routing, switching, NAT, firewall, wireless AP, DHCP service) then it's possible that this address is part of the default DHCP server scope of addresses it assigns to devices you connect on it.

If another device was connected while your workstation was shutdown, and it got assigned this IP, then maybe your router still associates it to that other device. When you try communicating outside of the subnet 192.168.5.0/24, then the returning traffic hits your router at 192.168.5.1, which in turns looks up your 192.168.5.107 in its ARP table and presumably associates it to with the wrong MAC address making it impossible to reach your workstation. You can normally clear that table by rebooting the device.

In general, it's advisable to setup static IP addresses that aren't part of any DHCP scope or use DHCP lease reservations.

user7429642

Posted 2017-12-18T23:15:17.613

Reputation: 1 121

Did you even read my question? It's not a cause of duplicate IP. – Adam Ježek – 2017-12-19T06:07:04.333

Asked: 2017-12-18T23:15:17.613

Viewed: 92 times

Active: 2017-12-19T01:28:30.753