What can an IP address be assigned to?
- A network interface, which is what I thought originally. (I seem to hear a network interface can have multiple IP addresses assigned to it, and if it is true, it doesn't affect that a IP address can be assigned to a network interface.)
- nothing, which is what I seem to hear https://unix.stackexchange.com/questions/508007/when-does-an-ip-address-not-need-to-be-assigned-to-a-network-interface where all loopback IP addresses (except 127.0.0.1) can work (be communicated with) without being assigned to network interface(s).
A host or network, which is implied by DNS resolution, and also by some sentences from Tanenbaum's Computer Network
The IP address 0.0.0.0, the lowest address, is used by hosts when they are being booted. It means this network or this host.
The address consisting of all 1s, or 255.255.255.255—the highest address—is used to mean all hosts on the indicated network.
Must a public IP address be assigned to a network interface?
Must a private IP address (i.e. 10.0.0.0 – 10.255.255.255/8, 172.16.0.0 – 172.31.255.255/12, 192.168.0.0 – 192.168.255.255/16) be assigned to a network interface?
Can a public IP address be assigned to more than one network interface?
Can a private IP address be assigned to more than one network interface?