Nmap is giving the option to the user to set a specific MTU (Maximum Transmission Unit) to the packet.This is similar to the packet fragmentation technique that we have explained above.During the scan that size of the nmap will create packets with size based on the number that we will give.In this example we gave the number 24 so the nmap will create 24-byte packets causing a confusion to the firewall.Have in mind that the MTU number must be a multiple of 8 (8,16,24,32 etc). You can specify the MTU of your choice with the command --mtu <number target>