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.
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I do remember two similar cases where the .0 and .255 also caused issues.
One was in the nineties with an internal office network (the time of Windows 95 and NT 4.0) with a little larger (512 addresses) /23 subnet. Clients which got the .255 or .0 through DHCP where not able to talk to system which where outside of that subnet.
And the second case was in an university environment (with public IP addresses on the clients) around 2005, where we got one large subnet of either /22 or even /21. There it took a little longer to see the issue, as almost everything was reachable without issue. But there was at least the website of a telecom provider in the country, which could not be reached from those computers. In that case we suspected that they may have a firewall in place which for “security” does block .0 and .255 addresses.
In both cases we stopped assigning .0 and .255 to any computer. I have no recent experience with this addresses, but it may still be a wise decision to exclude them from being used.