Set MTU of interface via powershell

Question

I'm trying to set the MTU for a physical interface programmatically on Windows 7:

PS> (Get-WmiObject -Class Win32_NetworkAdapterConfiguration | Where { $_.Description -match '^Red Hat.*#2' })

DHCPEnabled      : False
IPAddress        : {10.10.8.3, fe80::447d:38dc:bb39:f311}
DefaultIPGateway : 
DNSDomain        : 
ServiceName      : netkvm
Description      : Red Hat VirtIO Ethernet Adapter #2
Index            : 12

PS> (Get-WmiObject -Class Win32_NetworkAdapterConfiguration | Where { $_.Description -match '^Red Hat.*#2' }).SetMTU(9000)
Method invocation failed because [System.Management.ManagementObject#root\cimv2\Win32_NetworkAdapterConfiguration] doesn't contain a method named 'SetMTU'.
At line:1 char:113
+ (Get-WmiObject -Class Win32_NetworkAdapterConfiguration | Where { $_.Description -match '^Red Hat.*#2' }).SetMTU <<<< (9000)
    + CategoryInfo          : InvalidOperation: (SetMTU:String) [], RuntimeException
    + FullyQualifiedErrorId : MethodNotFound

Even though this method exists it still errors? Seriously?

Please help.

---

PS> (Get-WmiObject -Class Win32_NetworkAdapterConfiguration | \
    Where { $_.Description -match '^Red Hat.*#2' }) | Get-Member

returns, among other things:

MTU                          Property     System.UInt32 MTU {get;set;}

But trying to get or set it does nothing:

(Get-WmiObject -Class Win32_NetworkAdapterConfiguration | \
    Where { $_.Description -match '^Red Hat.*#2' }).MTU

Unless there's an Invoke-Magic or something I need to do.

---

As per Ryan's suggestion I had already changed the IPv4 MTU (and IPv6 MTU for good measure):

C:\>netsh interface ipv4 show subinterface "Local Area Connection 2"

   MTU  MediaSenseState   Bytes In  Bytes Out  Interface
------  ---------------  ---------  ---------  -------------
  9000                1       3686       6624  Local Area Connection 2

Seems well and good, but that only affects the subinterface, not the hardware interface:

That's even after a reboot.

Answer 1

Alright, this doesn't really answer your question, but I guess it contains some decent information anyway, so I'll leave it up. Hopefully someone has a better one.

Do:

(Get-WmiObject -Class Win32_NetworkAdapterConfiguration | 
Where { $_.Description -match '^Red Hat.*#2' }) | 
Get-Member

And observe the output. You will see that this instance does not actually contain a method named SetMTU, despite what that documentation says. Edit: Actually yours might. But my network interface does not have that. Looks like it's hardware-specific.

So I know what I'm about to do is cheating, but it works:

PS C:\> $AdapterName = $(Get-NetAdapter | Where { $_.Name -Match 'Ethernet'}).Name
PS C:\> netsh interface ipv4 set subinterface "$AdapterName" mtu=1500 store=persistent
Ok.

So like you said, that works for the interface, but maybe not for the hardware NIC. So I haven't truly answered your question.

You also mentioned Set-NetAdapterAdvancedProperty in your comments as well. However, I do not have an MTU setting there, either. Nor can I set the MTU on the device properties in the Windows GUI. I think the differences are hardware-specific.

Answer 2

$interface = (Get-WmiObject -Class Win32_NetworkAdapterConfiguration | Where { $.DefaultIPGateway -ne $null -and $.IPAddress -ne $null }) | select Description

$IFdesc = $interface.Description $AdapterName = $(Get-NetAdapter | Where { $_.InterfaceDescription -eq $IFdesc }).Name

netsh interface ipv4 set subinterface "$AdapterName" mtu=1360 store=persistent