I would really love to finish the first draft of the new Networking for Systems Administrators by the end of February.
On a traditional network, the first address in a subnet is the network address and the subnet’s last IP is the broadcast address. These addresses were designed to be unusable. If your office uses the network 203.0.113.0/24, the addresses 203.0.113.0 and 203.0.113.255 are unusable. There’s nothing magic about the numbers .0 and .255, they’re dictated by the subnet size.
Modern IP stacks no longer use the network and broadcast addresses for their original functions. Indeed, their original functions turned out to be problems. Most newer IP stacks allow assigning these addresses to hosts. The problem isn’t assigning these addresses, however—it’s what happens when an old device tries to communicate with the new device. When your decrepit office printer gets a request from 203.0.113.0, will it brick itself? Eventually this old gear will disappear, but for today hesitate to use top and bottom addresses.
You could still sponsor this book at https://www.tiltedwindmillpress.com/product/n4sa2e-sponsor/ .