I try to install a server from scratch with a fixed IP address. For installation I use the provided ISO of 18.04.3 and the installation agent of Ubuntu.
First I thought that my understanding of the subnet CIDR was wrong, but after I received credible information from https://networkengineering.stackexchange.com/questions/63499/how-to-interpret-subnet-mask I am sure that this is more a problem within Ubuntu.
When I enter 255.255.252.0/22 as subnet CIDR and 10.16.192.252 as the IP address I get the error message that 10.16.192.251 is not contained in 255.255.252.0/22. But a subnet calculator tells me that 10.16.192.1 - 10.16.195.254 would be part of the subnet.
