(Ob Humor: I read nanog via the web-based archive. Randy doesn’t have a .signature. I was going to google for his email. Such irony, timing.)
IIRC, 2511’s look the same as the aux on any Cisco box. For those, it is “CTRL-carat x”, where carat is ‘^’, shift-6 on most western keyboards.
Be careful not to just hit return next, since that is “continue” to telnet, defeating your correct “break” sequence’s intentions.
briand