Windows - IP MTU 값을 바꿀 수 있을까요?

MTU의 크기는 여러 가지 명령어를 통해 알아낼 수 있습니다.

// 리눅스의 MTU 확인
$ ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.28.96.233  netmask 255.255.240.0  broadcast 172.28.111.255
        inet6 fe80::215:5dff:fed3:44d5  prefixlen 64  scopeid 0x20<link>
        ether 00:15:5d:d3:44:d5  txqueuelen 1000  (Ethernet)
        RX packets 1613023  bytes 144197674 (144.1 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2374447  bytes 266671016 (266.6 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

// Windows의 MTU 확인
C:\temp> netsh interface ipv4 show subinterfaces

       MTU  MediaSenseState      Bytes In     Bytes Out  Interface
----------  ---------------  ------------  ------------  -------------
4294967295                1             0        281167  Loopback Pseudo-Interface 1
      1500                5             0             0  Local Area Connection
      1500                1       7572426      10258697  vEthernet (Default Switch)
      1500                1     451576156     127743835  vEthernet (WSL)

// C# 예제 코드

public const int IPPROTO_IP = 0;
public static int IP_MTU
{
    get
    {
        if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
        {
            return 73;
        }

        return 14;
/* 만약 WSL/Linux 환경에서 73으로 전달하면 실행 시 예외 발생
Unhandled exception. System.Net.Sockets.SocketException (92): Protocol not available
   at System.Net.Sockets.Socket.UpdateStatusAfterSocketErrorAndThrowException(SocketError error, Boolean disconnectOnFailure, String callerName)
   at System.Net.Sockets.Socket.GetRawSocketOption(Int32 optionLevel, Int32 optionName, Span`1 optionValue)
   at Program.Main(String[] args) in C:\temp\ConsoleApp1\ConsoleApp1\Program.cs:line 26
*/
    }
}

UdpClient client = new UdpClient("192.168.100.50", 60900);

byte[] buffer = new byte[4];
client.Client.GetRawSocketOption(IPPROTO_IP, IP_MTU, buffer);
int result = BitConverter.ToInt32(buffer, 0);
Console.WriteLine($"MTU_SIZE: {result}"); // 대개의 경우 1500 (Jumbo Frame 사용 시 9000)

# 파이썬 예제 코드 (리눅스에서 실행)

import socket
IP_MTU = 14  # 리눅스 14, 윈도우 73

s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.connect(('192.168.100.50', 60900))
mtu = s.getsockopt(socket.IPPROTO_IP, IP_MTU)
print('mtu', mtu)  # 대개의 경우 1500

$ python3 test.py
Traceback (most recent call last):
  File "test.py", line 14, in <module>
    mtu = s.getsockopt(socket.IPPROTO_IP, IP_MTU)
OSError: [Errno 107] Transport endpoint is not connected

// C#의 경우
System.Net.Sockets.SocketException: 'A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) no address was supplied.'

How To: Change and Check Windows MTU Size
; https://becomethesolution.com/how-to-change-and-check-windows-mtu-size

// 관리자 권한으로 실행

C:\Windows\System32> netsh
netsh> interface
netsh interface> ipv4

netsh interface ipv4> set subinterface "vEthernet (WSL)" mtu=1400 store=persistent
Ok.

netsh interface ipv4> set subinterface "vEthernet (WSL)" mtu=1501 store=persistent
The parameter is incorrect.