- September 19, 2019 at 11:30 AM #1917Santhosh Kumar DKeymaster
An MTU (maximum transmission unit) is the largest packet size that is being transferred in your internet connection. Your internet’s TCP (transmission control protocol) uses this MTU to determine the maximum size of each packet in any transmission.
If your connection’s MTU limit is set too high, it can cause fragmented packets and packet loss.
Let’s see how we can find and set the right MTU limit for your internet connection to make sure there are no packet losses.
Open Command Prompt and type the following command.
netsh interface ipv4 show subinterfaces
Enter. You will get a list of all your network adapters installed on your computer. As you can see, MTU values are listed on the left.
All PPP (point-to-point protocol) connections have a default MTU size of 1500 bytes and VPN connections have a default MTU size of 1400 bytes. 28 Bytes are reserved for IP/ICMP overhead. So, the effective MTU size is 1472 (1500-28).
To find the right MTU size for your connection, you have ping different MTU sizes starting from the default MTU. Keep reducing the MTU value to find the best suitable one that has a 0% packet loss.
Open a separate Command Prompt and type the following command to ping with an MTU size.
ping learntips.com -f -l 1472
-fmarks packets that should not be fragmented in the ping.
-l 1472sets the size of the packet.
If your reply is positive, then your current MTU size is good. In case, you received an error as shown in the above screenshot, then your packets are getting fragmented.
So, you have to find different MTU values until you get a positive reply. For example, if 1462 fails, try 1452 or less. But, don’t go below 1400.
Once you find a right value with a positive reply, try increasing the value 1 by 1. For example, if 1452 is right, then try again with 1453 and so on until you get errors again.
When you find a good MTU value, you can now set the MTU limit with this value. But you will have to add 28 back on to the value for IP/ICMP overheads. For example, if 1462 is successful, then 1490 is your MTU limit.
To set your new limit, in an elevated command prompt use the following commands.
For a wired connection, type the following command:
netsh interface ipv4 set subinterface "Local Area Connection" mtu=1490 store=persistent
(You can change the interface name to whatever you’re using. If you’re connected via “Local Area Connection 2” then use this instead and so on.)
For a wireless connection, use the following command:
netsh interface ipv4 set subinterface "Wireless Network Connection" mtu=1490 store=persistent
Don’t forget to add 28 on to the value you were using in your pings. So, if you were using a value of 1460 to ping, add 28 on, and the MTU value to set in the above commands will be 1488.
Simply hit Enter and the MTU value will be set. You have to restart your PC for the changes to be effective. Some routers also have an MTU value that can be set, such as Netgear routers can have an MTU value set in the WAN settings, then you can add your value here as well.
My wireless connection had some packet loss before. But after changing the MTP limit, I now get 0% packet loss, and web browsing is a breeze now.
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