Bride
Occasional Visitor
Hi,
I have a doubt about the MTU optimization process, following the procedure below.
I have to verify the parameters on my network equiments, any advice will be appreciated, I'm here for learn if possible:
ADSL WAN ROUTER - MTU 1444
ASUS RT-N66U ROUTER - MTU 1416
WINDOWS CLIENTS - MTU 1388
VPN SOFTWARE - MTU 1360
To find the correct MTU for your configuration you must run a simple DOS Ping test. You will simply send out ping requests and progressively lower your packet size until the packet no longer needs to be fragmented.
Please reference the following steps: The command for this ping test is ping www.snbforums.com -f -l xxxx where "xxxx" is the MTU size that you are testing, you can use also any well known, pingable domain like ping www.google.com
Step 1 Open a DOS prompt screen by clicking on Start>Programs>MSDOS-PROMPT. You can also use the Run Command by clicking on Start>Run then type in "cmd"
Step 2 At the DOS Prompt type in ping www.snbforums.com -f -l 1472 and hit Enter. Notice that the packet needs to be fragmented (packet needs to be fragmented but df set).
Step 3 Drop the test packet size down (10 or 12 bytes) and test again. Notice that the packet still needs to be fragmented.
Step 4 Drop the test packet size down more and test again until your reach a packet size that does not fragment. (reply from...).
Step 5 Once you have a test packet that is not fragmented increase your packet size in small increments and retest until you find the largest possible packet that doesn´t fragment.
Step 6 Take the maximum packet size from the ping test and add 28. You add 28 bytes because 20 bytes are reserved for the IP header and 8 bytes must be allocated for the ICMP Echo Request header. Remember: You must add 28 to your results from the ping test!
An example: 1444 Max packet size from Ping Test + 28 IP and ICMP headers 1472 is your optimal MTU Setting
I have a doubt about the MTU optimization process, following the procedure below.
I have to verify the parameters on my network equiments, any advice will be appreciated, I'm here for learn if possible:
ADSL WAN ROUTER - MTU 1444
ASUS RT-N66U ROUTER - MTU 1416
WINDOWS CLIENTS - MTU 1388
VPN SOFTWARE - MTU 1360
To find the correct MTU for your configuration you must run a simple DOS Ping test. You will simply send out ping requests and progressively lower your packet size until the packet no longer needs to be fragmented.
Please reference the following steps: The command for this ping test is ping www.snbforums.com -f -l xxxx where "xxxx" is the MTU size that you are testing, you can use also any well known, pingable domain like ping www.google.com
Step 1 Open a DOS prompt screen by clicking on Start>Programs>MSDOS-PROMPT. You can also use the Run Command by clicking on Start>Run then type in "cmd"
Step 2 At the DOS Prompt type in ping www.snbforums.com -f -l 1472 and hit Enter. Notice that the packet needs to be fragmented (packet needs to be fragmented but df set).
Step 3 Drop the test packet size down (10 or 12 bytes) and test again. Notice that the packet still needs to be fragmented.
Step 4 Drop the test packet size down more and test again until your reach a packet size that does not fragment. (reply from...).
Step 5 Once you have a test packet that is not fragmented increase your packet size in small increments and retest until you find the largest possible packet that doesn´t fragment.
Step 6 Take the maximum packet size from the ping test and add 28. You add 28 bytes because 20 bytes are reserved for the IP header and 8 bytes must be allocated for the ICMP Echo Request header. Remember: You must add 28 to your results from the ping test!
An example: 1444 Max packet size from Ping Test + 28 IP and ICMP headers 1472 is your optimal MTU Setting
Last edited: