Wireshark-users: Re: [Wireshark-users] Ethernet Port Speed
From: Kevin Cullimore <kcullimo@xxxxxxxxxx>
Date: Sat, 22 Sep 2012 18:34:42 -0400
On 9/9/2012 3:18 PM, Guy Harris wrote:
On Sep 8, 2012, at 10:53 AM, Ed Stuart <fcache@xxxxxxxxx> wrote:

I'm a newbie and I need to know if I can determine port speed settings of an ethernet port.
As packet transmission does not generally succeed unless both transmitting & receiving interfaces share an operational mode, the transmission of candidate details across the wire/medium occurs before any data that a driver should interpret as packets is sent. I'm not aware of any standardized provisions for including the outcome of Physical Layer link signaling/autonegotiation within packet data, so wireshark & related packet capturing tools may well be expected to fall short when attempting such a determination.
<snip>

In Windows XP, the Network Connections item in the Control Panel lets you see the properties of a "network connection"; these include the speed of the Ethernet port (at least on my virtual machine).  The ipconfig command, at least when run with /all, didn't report anything, but I guess that's not part of the IP configuration; I don't know if there's a command that will report it.  Windows 7 is similar, except that it's "Network and Sharing Center" rather than "Network Connections" in Control Panel.
Successful efforts I've encountered that worked/work within modern Microsoft operating system environments generally incorporated scripted queries to the registry or the WMI repository. The newer the NIC in question is, the greater the promise of success associated with recent bits of operational prestidigitation such as newer powershell Network Adapter Cmdlets such as Get-NetAdapterAdvancedProperty. Otherwise, this exercise remains every bit as neat, tidy and straightforward as one might expect when trapped within a Windows regime.