I've had good success running gettys on the various tty devices
associated with the "dz" driver: /dev/tty00, /dev/tty01, etc.
The man page for dz references dialup devices which go by the names
like /dev/ttyd0 and /dev/ttyd1.  Then the tty(4) man page states:

     Each hardware terminal port on the system usually has two
     terminal special device files associated with it in the directory
     /dev/ (for example, /dev/tty03 and /dev/dty03).

     The /dev/ttyXX special file is used for dial-in modems and
     terminals.  When a user logs into the system on one of these
     hardware terminal ports, the system has already opened the
     associated device and prepared the line  for normal interactive
     use (see getty(8)).

     The /dev/dtyXX special file is a SunOS-compatible dial-out
     device. Unlike the dial-in device, opening the dial-out device
     never blocks.  [...]

I found that there are neither /dev/ttydX or /dev/dtyXX devices under
/dev/ on my VAXes.  I also found that MAKEDEV doesn't know how to create
these devices.  I was sort of hoping to use one of my VAXes as a
terminal server, using cu on the appropriate devices to get access to
the consoles of my other systems, but it doesn't look like this is
possible.

Or is it?

-brian.