# dynamic interfaces need not exist at load-time, but names must start # with a letter. catches common macro typo cases of ($ext_ip) vs. ($ext_if) nat on lo0 from any to any -> (lo0) nat on lo0 from any to any -> (lo0:0) nat on lo0 from any to any -> (nonexistant0) nat on lo0 from any to any -> (nonexistant0:0) nat on lo0 from any to any -> (10.1.2.3) nat on lo0 from any to any -> (10.1.2.3:0)