Sort IPv4 and IPv6 Addresses Correctly

by Mar 14, 2018

When you try and sort IPv4 addresses via Sort-Object, this fails:

 
PS> '10.1.2.3', '2.3.4.5', '1.2.3.4' | Sort-Object
1.2.3.4
10.1.2.3
2.3.4.5

This is no surprise because the data is of type “string”, so Sort-Object uses alphanumeric sorting. In the previous tip we showed how you can cast the data to [Version] and pretend you are sorting software versions:

 
PS> '10.1.2.3', '2.3.4.5', '1.2.3.4' | Sort-Object -Property { $_ -as [Version] }
1.2.3.4
2.3.4.5
10.1.2.3

However, this fails with IPv6 addresses because they cannot be turned into a version number:

 
PS> '10.1.2.3', 'fe80::532:c4e:c409:b987%13', '2.3.4.5', '2DAB:FFFF:0000:3EAE:01AA:00FF:DD72:2C4A', '1.2.3.4' | Sort-Object -Property { $_ -as [Version] }

fe80::532:c4e:c409:b987%13
2DAB:FFFF:0000:3EAE:01AA:00FF:DD72:2C4A
1.2.3.4
2.3.4.5
10.1.2.3

Converting IPv6 addresses to [Version] using the operator -as yields NULL, which is why IPv6 addresses appear at the top of the list in exactly the order they were fed into Sort-Object.

To sort IPv6 addresses, the default alphanumerical sorting would be adequate, so let’s just differentiate, and when an IPv6 address is encountered, use its string value for sorting:

$code = {
    $version = $_ -as [Version]
    if ($version -eq $null) { "z$_" }
    else { $version }
} 

'10.1.2.3', 'fe80::532:c4e:c409:b987%13', '2.3.4.5', '2DAB:FFFF:0000:3EAE:01AA:00FF:DD72:2C4A', '1.2.3.4' | Sort-Object -Property $code

Now the result looks nice and clean:

 
10.1.2.3
2.3.4.5
1.2.3.4
2DAB:FFFF:0000:3EAE:01AA:00FF:DD72:2C4A
fe80::532:c4e:c409:b987%13

Note how the code adds a “z” to the string representation of IPv6 addresses. This ensures that IPv6 addresses will appear at the bottom of the list. If you’d like them to be at the top of the list, try this:

$code = {
    $version = $_ -as [Version]
    if ($version -eq $null) { "/$_" }
    else { $version }
}

Since “/” has a lower ASCII value than “0”, now IPv6 addresses appear at the top of the list:

 
2DAB:FFFF:0000:3EAE:01AA:00FF:DD72:2C4A
fe80::532:c4e:c409:b987%13
1.2.3.4
2.3.4.5
10.1.2.3

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