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How to find windows network adapter in registry

show network adapters GUID and find the interface in registry

Windows assigns a GUID to each network adapter, where all network adapters, such as the Ethernet adapter, wireless adapter or virtual adapters, and also the Bluetooth device have their own GUID. In case of modify parameters on a network adapter, for example, if there is no option in the network settings, as they cannot be found under the physical adapter type or with adapter name in the registry.

A relatively simple method is the following procedure. The first thing to do is to open the Services console by press the Win+R keys and type services.msc

In the open Windows Services console you start the service Wired AutoConfig if it is not already running.

The next step is to open a command prompt by pressing Win+Rcmd

In the command prompt, paste the following command line with copy & paste and press the Enter key.

netsh lan show interfaces
netsh wlan show interfaces

To get the GUID of the wireless adapter, the service WLAN AutoConfig must be started.

The output appears similar to the following, the number of interfaces may vary depending on which hardware and software components the system has.

C:\>netsh lan show interfaces

There is 1 interface on the system:

    Name             : Ethernet
    Description      : Intel(R) Ethernet Connection (7) I219-V
    GUID             : 8b4f4148-7940-4d76-a0dd-00ddf89dff59
    Physical Address : 98-FA-9B-04-5B-59
    State            : Connected. Network does not support authentication.

C:\>netsh wlan show interfaces

There is 1 interface on the system:

    Name                   : WLAN
    Description            : Intel(R) Dual Band Wireless-AC 3165
    GUID                   : a7dd2b68-eaef-42cc-884d-716374b22520
    Physical address       : a0:51:0b:2c:ad:f8
    State                  : disconnected
    Radio status           : Hardware On
                             Software On

As here, all network and wireless adapters are displayed, in the name or description can see which network adapter has which GUID directly below the description.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NetBT\Parameters\Interfaces

Just the GUID now found, the corresponding network adapter can be found in Registry Editor.

Maximum Transmission Unit (MTU) Check

The Maximum Transmission Unit describes the maximum packet size of a protocol in the network layer of the OSI model, which can be transmitted in networks without fragmenting the frames in the data link layer. This packet size fits into the payload of the data link layer protocol.

How to check optimal MTU size for Routers

To check the MTU of a path, you have to pass the parameter -f to ping to set the “don’t fragment bit (DF-Bit-Set)” for the ICMP test packets in the IPv4 header, only then you will receive a message if the MTU is exceeded.

The ICMP Package and MTU size

Run Ping in the Windows command prompt to determine the MTU size of a desired path.

The parameter -f specifies that the packages are not fragmented.
The size of the send buffer is specified with -l.

C:\> ping -4 -f 1.1.1.1 -l 1473

Pinging 1.1.1.1 with 1473 bytes of data:
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.

Ping statistics for 1.1.1.1:
    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

As the above results show, the packets should be fragmented. If the -f parameter were omitted, the ping would respond with fragmentation, which we don’t want.

If you don’t get an reply but see “Packet needs to be fragmented but DF set.” you’ve not found the maximum ping size.

  Hint. It is best to gradually reduce the ping with the MTU value, in steps of 10+/-10 (e.g. 1472, 1462, 1440, 1400) until a packet size has been reached that is no longer fragmented and a response is received.

C:\> ping -4 -f 1.1.1.1 -l 1472

Pinging 1.1.1.1 with 1472 bytes of data:
Reply from 1.1.1.1: bytes=1472 time=7ms TTL=56
Reply from 1.1.1.1: bytes=1472 time=7ms TTL=56
Reply from 1.1.1.1: bytes=1472 time=7ms TTL=56
Reply from 1.1.1.1: bytes=1472 time=7ms TTL=56

Ping statistics for 1.1.1.1:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 7ms, Maximum = 7ms, Average = 7ms

The above results indicate that the packets will not be fragmented.

To get the right MTU size, take 1472 and add 28 to it. In the example above, 1472 is the correct value, and the size is 1500 for the network in which you work.

  Calculation: 8 bytes for the ICMP-header + 20 bytes for the IP-header + 1472 bytes for the ICMP-payload:  8 + 20 + 1472 = 1500

The Control Message Protocol Protocol (ICMP) in layer 3 of the network layer, which is used by ping to send a message via the ICMP payload, which is encapsulated with the IP header. The MTU cannot exceed the size of the ICMP packet of 1500 bytes.

ICMP packet at Network layer

IP headerICMP headerICMP payload sizeMTU (1500)
20 bytes8 bytes1472 bytes
(maximum)
20 + 8 + 1472 = 1500

ICMP packet at Data Link layer

Ethernet
header
IP headerICMP headerICMP payload size  MTU (1514)
1420 bytes8 bytes1472 bytes
(maximum)
14 + 20 + 8 + 1472 = 1514

Note. default size of ICMP payload is 32 bytes and the maximum is 1472, if the size of the payload packet is greater than 1472 then packet gets fragmented into small packets.

ICMP Message Packet decoding in Wireshark

The ICMP packet sent by the source machine is an echo request. The figure shows that ICMP query code 8 responds to the ping request.

Using Linux Ping set don’t fragment bit (DF-Bit-Set) in the Linux Shell and macOS Terminal

Linuxping -M do -s 1472 1.1.1.1
macOSping -D -s 1472 1.1.1.1
Linux Ping DF-Flag to set don’t fragment (DF)

Use Linux ping in a terminal will using DF-bit-set do not fragment message.

$ ping -M do -s 1473 1.1.1.1
PING 1.1.1.1 (1.1.1.1) 1473(1501) bytes of data.
ping: local error: Message too long, mtu=1500
ping: local error: Message too long, mtu=1500
ping: local error: Message too long, mtu=1500
^C
--- 1.1.1.1 ping statistics ---
3 packets transmitted, 0 received, +3 errors, 100% packet loss, time 31ms

Typical MTU sizes

MediumMTU in Bytes
Ethernet1500
PPPoE1492
VPN encapsulated1420
ATM4500