If you have a device (webcam, printer, PC, server…) that you can connect from from most computers on your network but not others, there are two common reasons for you to investigate:
- The device has a firewall or antivirus product that is actively blocking the traffic
- The device has a misconfigured network, specifically the Subnet Mask
In my case, I was working on a security appliance that was using a statically assigned 255.255.255.0 for the subnet mask when it should have been 1 class C larger 255.255.254.0. This meant that all of the PC’s with an IP in the lowest range (10.10.10.1-255) could connect fine but PC’s in the second range (10.10.11.1-255) could not. It was a simple fix to correct the subnet mask but it took me 2 frustrating hours to figure out so I thought my pain might be your gain.
TROUBLESHOOTING NETWORK CONNECTION PROBLEMS TOP 10:
- Try to ping the IP address (not the name) of both the PC and the device you cannot connect to, from themselves
. - Try to ping the IP address (not the name) of both the PC and the device you cannot connect to, from a different PC, preferably in a different location (different floor, office…)
. - Turn off any firewalls, AV or Malware protection (yes, just for a minute so you can test)
. - Check the Subnet mask on both systems
. - In an elevated CMD prompt, try TRACERT <IPADDRESS> to see where the traffic stops
. - In an elevated CMD prompt, try NETSTAT -R to list off the routes and see if anything seems odd
. - If pinging the hostname is not working but the IP address is, you may have something misconfigured in your DNS or your HOSTS file so check your HOSTS file stored under C:\Windows\System32\drivers\etc
. - If the device you cannot connect to has a DHCP address, assign it a static IP, Subnet and DNS
. - Reboot both the PC and the device to clear any routing issues or crashed services
. - If all else fails, the problem may be in a network switch between the PC and the failing device so manually clearing the ARP table on that switch (or switches) or just rebooting that switch may help
3 Comments
petejonesbus · January 7, 2022 at 12:36 am
I have issues where some devices can ping and some can’t. Oddly, these are intermittent issues too. the devices concerned are connected via WiFi
Ian Matthews · January 19, 2022 at 8:39 pm
Can you ping the IP address?
Nom De Guerre · February 4, 2019 at 8:08 am
I have one of these at the moment. Except it’s not a subnet mismatch/difference or device Firewall/ACL/Security settings (device has an admin password set, but no other security settings are enabled). I’m having trouble with an HP LaserJet Pro M201dw. I can ping it just fine from my Windows workstation and a MacBook, but not from a Windows print server or some other workstations. The print server had been able to send jobs to the printer until fairly recently, it started frequently appearing as offline. Yet I can set up a network connection and print with no trouble from a workstation that can ping the printer. The M201dw connects wirelessly to a UniFi AP HD. I’m not using UniFi Security Gateway, firewall rules. Pretty basic set up.
I told the main user of the printer I should have the problem resolved by end of 2019. 😉