Incorrect DHCP range validation
Our office setting uses public IPv4 chunk:
- router IP: x.x.x.97
- netmask: 255.255.255.224
- DHCP start: 100
This results into DHCP leases starting at x.x.x.100 (shown experimentally) and not at x.x.x.196 as these calculations expect (if I read them correctly). The validation can never succeed in our case, as netmask ends the range at .127.
Typically people won't hit this, as they use netmask ending in .0 (private ranges typically).