One benefit is related to DNS. If you assume fbsrv is an internal network, you have to be on the company network in order to access it. This automatically restr

One benefit is related to DNS. If you assume fbsrv is an internal network, you have to be on the company network in order to access it. This automatically restricts everything on fbsrv.com to company machines on the VPN or things in the datacenter. Now when you see db1.fbsrv.com you know that it's your database server on your private network, and none of that traffic is going across the internet. You can do the same thing with subdomains (e.g. internal.foobar.com), and then tree off of that (db1.site1.internal.megacorp.com), but that gets confusing.