How to Find Your MTU Settings
- 1). Open a command window. In Windows NT/2000/2003/ XP, this is done by clicking the Windows "Start" button, going to "Programs," then "Accessories," then "Command Prompt."
- 2). Type the command:
"ping -f -l 1472 232.151.20.120"
into the command window. The numbers "232.15.20.120" refer to the IP address you are communicating with and might be different depending on your circumstances. Note the packet loss under "ping statistics." - 3). Increase the number from 1472 (which is the size of the packet in bytes) to a larger number by a set amount (say five) if there is zero percent packet loss. However, if there is 100 percent packet loss, then you decrease the number by a set amount. For example, if there is 100 percent packet loss for the previous command, then you might want to decrease the packet size by 20, giving the command:
"ping -f -l 1452 232.151.20.120" - 4). Continue increasing or decreasing the byte size using the "ping -f -l" command until you converge on the maximum value where there is zero percent packet loss and any more bytes added to the packet result in 100 percent packet loss. For example, if a byte size of 1,464 results in zero percent packet loss, but 1,466 results in 100 percent packet loss, then 1,464 is the desired number.
- 5). Add 28 to the maximum byte size that can be transmitted. For example, if 1,464 is the maximum byte size that is transmitted without loss, adding 28 to this gives 1,492. This is the MTU of your network.