Windows 2008 R2 MTU Setting
Changing the default Windows 2008 R2 MTU
1. First up we need to find the correct MTU to set, without knowing this we’ll most probably be way off. As an example, I want to find the optimum MTU when heading out to the internet. I’ll open a command prompt and ping www.google.com with the following switches -f which instructs ping to not fragment the packet, and -l with a packet size of 1500 of less. The key here is to find the next available packet size before the packet needs to be fragmented, and that is what we want to set out MTU as.
In the picture below, you can see that pinging google with a packet size of 1465 bytes causes the packet to fragment, however pinging google with a packet size of 1464 does not fragment the packet. Therefore the optimum MTU for my Windows 2008 R2 server heading out to the internet is 1464.
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Good tutorial 🙂
Don’t forget that the “-l” parameter of the ping command concerns the amount of datas sent with the packet. Add 8 bytes for the ICMP header and 20 for the IP header to have the IP packet’s full length. DSL connection very often needs the MTU to be set to 1492 (PPPoE).
Does this require a reboot to take effect? I was trying to change the MTU to 1200 but I can still ping the address with a MTU size of 1472.
I would reboot the server after the change