October 31, 2016

PowerShell – Find the appropriate network packet (MTU) size

While working with the SQL guys from my current customer, we found that we needed to know which MTU size we could configure.
To understand what MTU size, or packet size, are and how they can impact SQL Server, I suggest you do some serious homework.
Changes in this can greatly impact the performance of SQL Server, both in a positive and negative way.

Oh well, here’s a script that will help you get an MTU value based on the network configuration you have in your environment (routers, switches, NICs, etc.):

$UpperBoundPacketSize = 4096
do {
    Write-Output "Testing packet size $UpperBoundPacketSize"
    $PingOut = ping $IpToPing -n 1 -l $UpperBoundPacketSize -f
    $UpperBoundPacketSize -= 1
} while ($PingOut[2] -like "*fragmented*")

$UpperBoundPacketSize += 1
$Mtu = $UpperBoundPacketSize + 28

New-Object -TypeName PSObject -Property @{
    MTU = $MTU
}

$UpperBoundPacketSize = 4096

do {

Write-Output "Testing packet size $UpperBoundPacketSize"

$PingOut = ping $IpToPing -n 1 -l $UpperBoundPacketSize -f

$UpperBoundPacketSize -= 1

} while ($PingOut[2] -like "*fragmented*")

$UpperBoundPacketSize += 1

$Mtu = $UpperBoundPacketSize + 28

New-Object -TypeName PSObject -Property @{

MTU = $MTU

}

2 comments

Guido Jakobs says:

November 21, 2016 at 16:17

Hoi Jeff

Lol, Ik heb zelf twee jaar geleden ook zo’n scriptje gemaakt.

https://gallery.technet.microsoft.com/scriptcenter/Find-the-Biggest-MTU-size-ff1c6069
Jeff Wouters says:

November 25, 2016 at 10:51

Hoi Guido,
Ow, dan had je die uitdaging eerder 😀
Jeff.

JeffOps

PowerShell – Find the appropriate network packet (MTU) size

2 comments

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