While you can have more than that , it depends on your traffic patterns and useage . I think for the most part though a /24 is a very good number to work with and keeps your broadcast domain to a good size.

Hi!

It always depends on your requirement. It actually is not a rule of thumb, I guess it's just that a /24 network is what always comes to your mind first when configuring a network. Setting up a number of host on a VLAN should always be based on what is required with some considerations for future expansions.

Hope this helps,

Regards,

Albert