Registry Guide for Windows

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Registry tweaks, tricks & hacks to optimize, enhance and secure Microsoft Windows.

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Home > Network > Protocols > TCP-IP

(Windows NT/2000/XP)
Enabling the setting causes TCP to attempt to discover the Maximum Transmission Unit (MTU or largest packet size) over the path to a remote host. By discovering the Path MTU and limiting TCP segments to this size, TCP can eliminate fragmentation at routers along the path that connect networks with different MTUs.

This tweak can be easily applied using WinGuides Tweak Manager.
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Open your registry and find or create the key below.

Create a new DWORD value, or modify the existing value, called "EnablePMTUDiscovery" and set it according to the value data below.

Exit your registry, you may need to restart or log out of Windows for the change to take effect.


(Default)	REG_SZ	(value not set)
EnablePMTUDiscovery	REG_DWORD	0x00000001 (1)


	HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\P...

Registry Settings

System Key: [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters]
Value Name: EnablePMTUDiscovery
Data Type: REG_DWORD (DWORD Value)
Value Data: (0 = false, 1 = true)

Disclaimer: Modifying the registry can cause serious problems that may require you to reinstall your operating system. We cannot guarantee that problems resulting from modifications to the registry can be solved. Use the information provided at your own risk.

Last Modified: May 14, 2002