You'll struggle to come up with something truly dynamic (and elegant) in one cell without use of VBA (UDF) and/or 3rd party add-in like morefunc.xll (MCONCAT function)

In UDF terms, the below stored in a Module

Option Explicit
Option Compare Text
Function Switches(strRept As String, rngRept As Range, Optional strDelim As String) As String
Dim lngRept As Long
If strDelim = "" Then strDelim = ","
For lngRept = 1 To rngRept.Value Step 1
    Switches = Switches & strDelim & Replace(strRept, "[X]", lngRept)
Next lngRept
Switches = Replace(Switches, strDelim, "", 1, 1)
End Function
in a Macro Enabled file can be used along lines of:

B2: =SWITCHES("GigabitEthernet, [X]/0/1 - 48",$A2)
where [X] denotes the placeholder position

If you wanted to use an alternative delimiter (to comma) you can explicitly pass the otherwise optional 3rd argument, eg to use :

B2: =SWITCHES("GigabitEthernet, [X]/0/1 - 48",$A2,":")