When you have not-short time with Cisco router/switch, you know “how helpful” the question mark “?” is. However is it really that helpful, my personal experience is “Yes, sometime… and also confusing sometime…” Here is an example to show my point, if you type-in following on a router/switch with 11.1 or newer IOS:
router(config)# aaa ?
new-model Enable NEW access control commands and functions. (Disables OLD commands.)
For someone who knows what s/he is doing, then the router is just helping her/him remember the command option and warning about the old login commands will be disabled. So person who is doing this needs to create local or remote accounts to prevent be locked out of device.
However, if someone is configuring AAA for the first time, does the context help make sense? What does it mean by “Disables OLD commands”? Which one(s) is/are THE OLD commands …
BTW, here below is also a neat “back-door” in case remote and/or local user database died (Not sure how can functioning device has a dead local user database though)
router(config)# aaa authentication login NO-LOGIN none
router(config)# line con 0
router(config-line)# login authentication NO-LOGIN