Wasn't as complicated as I feared. Cool little frog analogy, although you have to know a bit about subnetting etc. to really get the whole picture. Overall, helpful and concise video :)
If you mean why 128.156.40.12/24 became 128.156.40.0, then this happens because of the /24-Subnetmask. /24 means that the first 24 Bits of the 32 IP Bits are "1" and the others "0". All those which are "0" can be used for Hosts (Computers, Routers...), the other 24 for the Network-Adress. To get to 128.156.40.0 you have to calculate the following: IP(128.156.40.12) AND /24-Mask(255.255.255.0). The AND is a bit-operator, so you have to calculate what e.g. 128 is in Bits (it should be 1000000). if you do that for any of those numbers between the dots, then you can apply the AND operator and then outcome are the 32 Bits which represent 128.156.40.0 Hope i could help.
Dreckbob Bratpfanne 128.156.40.12/24 /24= 255.255.255.0 11111111.11111111.11111111. | 00000000 128.156.40. | 0 That’s why it’s 128.156.40.0 Lowest/highest available (valid) adresses would be 128.156.40.1 and 128.156.40.254, since 0 is network address and 255 is broadcast address.
Because the fixed bits of the address in row 4 match with the ip of the destination, but because the amount of matched fixed bits in row 2 is bigger the router will choose for the address in row 2.