i'd always be careful when messing with things like MTU changing this on a router can make packet loss a hell of a lot worse your ISP should do this as part of its PPP session each ISP is slightly different as their infrastructure differes from vendor to vendor Cisco prefer lower MTU over Juniper, port size also comes into play as well.
however if you wish get a better understanding of how these things work you can test it all yourself.
example below an extreme MTU 1500 for example causes to much Data to be sent in one single frame, I have sent the data size to 1500 (MTU) as you can see it breaks the ICMP. ive set a -f switch as its windows which sets a DO NOT FRAGMENT flag and the -l being the size.
I know my optimal MTU already but you can tweak it to find your (almost) optimal.
In my actual router its set to 1467 not sure why as these size chunks in the frame cause packet loss when playing online games, so i always lower it by 5 (ish)
So these tools are great but its always good to understand what you are doing, just like overclocking your cards you can break shit so its best to understand what you are doing before doing it
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