Infrastructure addresses definition

How do you define infrastructure addresses in your network? Ok, probably router loopbacks are some of them. Router LANs also. But what about addresses used on WAN (or LAN p2p) links that are used for interconnections with customers? What about addresses used for public servers (dns, mail, web, etc)? Do you consider these as infrastructure addresses? If yes, how do you define your iACLs with these included? Regards, Tassos