Name based virtual hosts on specific IP address

Question

The Apache Virtual Host documentation says :

You can alternatively specify an explicit IP address in place of the * in <VirtualHost *:80> directives. For example, you might want to do this in order to run some name-based virtual hosts on one IP address, and either IP-based, or another set of name-based virtual hosts on another address.

These virtual host blocks get executed on a server which obviously has 1 IP address. Why would there be a necessity to mention different IP address in these VirtualHost directives?

Thanks

Answer 1

These virtual host blocks get executed on a server which obviously has 1 IP address.

Servers don't obviously have a single IP address.

A machine (any machine, not only server hardware) may have multiple physical network cards, and therefore multiple IP addresses. An operating system may also use multiple virtual network interfaces and thus have multiple IP addresses. The ability to use a specific IP address is not only not-strange, it's very much desirable.