Changing Windows MTU: Difference between revisions

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<indicator name="Front">[[File:Menu-packet.svg|link=:Category:MTU|30px|Back up to the MTU Page]]</indicator>

[[Category:MTU]]

The MTU (Maximum Transmission Unit) is the size of the largest network packet that can be transferred in a single network transmission without any fragmentation happening.

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Sometimes you may have a reason to change the MTU on your windows computer. Here is how.

We have a separate page on testing your [[MTU]].

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===1. Open Command Prompt as Administrator===

# Click start

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Sometimes you may have a reason to change the MTU on your windows computer. Here is how.

# Type cmd

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# On the Right hand side, click 'Run as administrator'

We will show you how to show the existing MTU, and then how to change it, and then how to revert it back to what it was originally. We're using Windows 10 in this example.

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===1. Open Command Prompt, as Administrator===

# Click <SyntaxHighlight inline>start</SyntaxHighlight>

# Type <SyntaxHighlight inline>cmd</SyntaxHighlight>

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# On the Right hand side, click <SyntaxHighlight inline>'Run as administrator'</SyntaxHighlight>

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===2. Show the current MTU and the interface name ===

#Enter in the command: <SyntaxHighlight inline>netsh interface ipv4 show subinterfaces </SyntaxHighlight>

#Make a note of the existing MTU (probably 1500)

#Make a note of the existing MTU (probably <SyntaxHighlight inline>1500</SyntaxHighlight>)

#Make a note of the interface name - eg Ethernet

#Make a note of the interface name - eg <SyntaxHighlight inline>Ethernet</SyntaxHighlight>

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#Enter the command: <SyntaxHighlight inline>netsh</SyntaxHighlight>

#Then: <SyntaxHighlight inline>interface</SyntaxHighlight>

Then: <SyntaxHighlight inline>ipv4</SyntaxHighlight>

#Then: <SyntaxHighlight inline>ipv4</SyntaxHighlight>

Then: <SyntaxHighlight inline>set subinterface "Ethernet" mtu=1320</SyntaxHighlight>

#Then: <SyntaxHighlight inline>set subinterface "Ethernet" mtu=1320</SyntaxHighlight>

Then: <SyntaxHighlight inline>exit</SyntaxHighlight>

#Then: <SyntaxHighlight inline>exit</SyntaxHighlight>

The screenshot shows all these commands being run...

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===6. Reverting back===

# ~~restarting~~ the computer should change the MTU back to default

# Restarting the computer should change the MTU back to default

# Or, you can run the commands above, but set <SyntaxHighlight inline>1500</SyntaxHighlight> instead of <SyntaxHighlight inline>1320</SyntaxHighlight>

===7. Keeping the MTU change permanent===

If you want to keep thje lower MTU even after a reboot, then re-run the commands, but when you come to change the MTU add <SyntaxHighlight inline>store=persistent</SyntaxHighlight> to the command.

eg <SyntaxHighlight inline>set subinterface "Ethernet" mtu=1320 store=persistent</SyntaxHighlight>