On old router
line aux 0
transport input all
exit
and now see the line number of aux port:
show line
it will be number X (1 or 5 or whatever)
then find any live ip (fe. inside IP) address on the router and do reverse telnet like this
telnet 2000+x
if x is 5 then 2000+5=2005
so it's telnet 2005
M.
Hope that helps rate if it does