Certain security updates may cause the MTU to decrease. which significantly reduces system performance and leads to the inability to connect to certain web resources. Receiving an ICMP warning with the text destination unreachable is indicative of a similar problem.
Instructions
Step 1
Click the Start button to bring up the main system menu and go to Run to launch the Registry Editor tool to enable PMTU Black Hole detection.
Step 2
Enter regedit in the Open field and click OK to confirm the command.
Step 3
Expand the registry key
HKEY_LOCAL_MACHINE / System / CurrentControlSet / Services / Tcpip / Parameters
and select it.
Step 4
Specify the "New" item in the "Edit" menu of the upper toolbar of the program window and select the DWORD string value.
Step 5
Enter the value EnablePMTUBHDetect and press the Enter key to confirm your choice.
Step 6
Select the "Change" item in the "Edit" menu of the upper toolbar of the program window and enter the value "1" in the "Value" field.
Step 7
Click OK to confirm the command and close the Registry Editor utility.
Step 8
Restart your computer to apply the selected changes, and return to the Registry Editor tool to disable the PMTU detection feature.
Step 9
Expand the registry branch
HKEY_LOCAL_MACHINE / System / CurrentControlSet / Services / Tcpip / Parameters
and select it.
Step 10
Specify the "New" item in the "Edit" menu of the upper toolbar of the program window and select the DWORD string value.
Step 11
Enter the value EnablePMTUDiscovery and press Enter to confirm your choice.
Step 12
Select the "Change" item in the "Edit" menu of the upper toolbar of the program window and enter the value "0" in the "Value" field.
Step 13
Click OK to confirm the command and close the Registry Editor utility.
Step 14
Restart your computer to apply the selected changes, and return to the Registry Editor tool to manually specify the MTU value for the network interface.
Step 15
Expand the registry branch
HKEY_LOCAL_MACHINE / System / CurrentControlSet / Services / Tcpip / Parameters / Interfaces \
and select it.
Step 16
Specify the "New" item in the "Edit" menu of the upper toolbar of the program window and select the DWORD string value.
Step 17
Enter the MTU value and press the Enter key to confirm your choice.
Step 18
Select the "Change" item in the "Edit" menu of the upper toolbar of the program window and enter the MTU value in the "Value" field.
Step 19
Click OK to confirm the command and close the Registry Editor utility.
Step 20
Restart your computer to apply the selected changes.
