Find the path Maximum Transfer Unit(MTU) of a network using Mturoute tool

mturoute.exe is a small command line application that uses ICMP pings of various sizes in order to determine the MTU values on the path between itself and the target system. It also includes a “traceroute” mode where it will attempt to determine the lowest MTU between the local host and each hop in the communication.

More details about the Mturoute tool :

Requiements:

  • Microsoft Windows OS

Note

  • The Mturoute tool can be used to find the path MTU size of the IPv4 packets passing through the Network.
  • The value of MTU for the network is measured in Bytes.

Path Maximum Transmission Unit(MTU)

The path Maximum Transmission Unit (MTU) is the largest size of the data packet that can travel through a network without being fragmented.

Proper configuration of MTU of the network adapter in Windows 10 & 11 OS can prevent the fragmentation of data packet when it travels through the internet and has the following benefits:

  • Helps in increasing the internet data transfer speed and in reducing network latency.
  • It solves internet connectivity issues and slow internet speed on some applications.

MTU Command line tools usage

Download mturote tool and install it

  1. First download “mturoute.exe” from the following website : https://www.elifulkerson.com/projects/mturoute.php

2. Copy the “mturoute.exe” to the folder C:\windows\system32.

Run Command Prompt(CMD) or PowerShell

Command prompt or Powershell can be used to run the command line tool mturoute.exe.

To run the Command prompt in Administrator mode do the following:

  • Click on the Start menu and type “cmd”.
  • Right-click on Command prompt app and select “Run as administrator“.

To run the Powershell in Administrator mode do the following:

  • Open Windows Start Menu > Windows Powershell.
  • Right-click the Windows Powershell and select “Run as Administrator“.

Find MTU of the Internet using mturoute

Things to note before using mturoute:

  1. The Network Interface card(NIC) is used to connect to the internet. It could be Ethernet NIC or a wireless NIC. The Network Interface card(NIC) must be a physical card and not a virtual one.
  2. The website or IPv4 address of the remote host on the internet. It’s better that you choose a website or IPv4 which is located farthest from your location. When a website hosted on another continent is used the route includes multiple routers which are helpful in finding the optimal path MTU.
  3. Internet Service Provider(ISP): You may have subscribed to multiple ISPs for an Internet connection. Each of the ISP networks may have a different MTU. In this case, if the Network Interface card(NIC) connects to the internet using various ISP’s services will you must find out MTU for each of the ISPs. You will have to set the MTU for the Network Interface card(NIC) which is the lowest among multiple ISPs.

Example:

My computer connects to the internet using two ISP. My Wireless network Interface Card is used to connect to both of the ISPs. So I Need to find the MTU is both the ISP. Then I will use the lowest MTU.

To find MTU of ISP_1 use the following command:

  • Connect to the Internet using ISP_1.
  • Start Command Prompt or Powershell.
  • Run the command: mturoute http://www.bing.com
  • Run the command : mturoute 8.8.8.8

Path MTU of ISP_1: 1480 bytes

To find the MTU of ISP_2 use the following command:

  • Connect to the Internet using ISP_2.
  • Start Command Prompt or Powershell tool.
  • Run the command: mturoute http://www.google.com
  • Run the command : mturoute 1.1.1.1

Path MTU of ISP_2: 1400 bytes

The optimal size of MTU that should be used for my Network Interface Card is 1400 bytes.

Find which Router is limiting the path MTU of the Internet using mturoute

Mturoute tool can also be used to find the router that is limiting the MTU of the network. Mturoute “traceroute” mode, performs the MTU test for each hop between your computer and the specified host.

Certain Routers may not respond to this command. In that case, this tool cannot find the MTU for those routers.

  • Usage: mturoute [-t] host

Example

Command to find the Router dictating the MTU: mturoute -t http://www.bing.com

Router with IPv4 address 10.72.46.58 is limiting the path MTU size to 1400 bytes.

Command to find the Router dictating the MTU: mturoute -t 8.8.8.8

Router with IPv4 address 10.72.46.50 is limiting the path MTU size to 1400 bytes.

Command to find the Router dictating the MTU: mturoute -t 8.8.8.8

Router with IPv4 address 223.235.31.255 is limiting the path MTU size to 1480 bytes.

Command to find the Router dictating the MTU: mturoute -t http://www.bing.com

Router with IPv4 address 223.235.31.255 is limiting the path MTU size to 1480 bytes.

Reference