Add a login banner to your Cisco router

A login banner is displayed whenever someone connects to the router by telnet or console connections.

The syntax for the banner command is:

banner motd {char} {banner text} {char}

where {char} is a special delimeter character that does not exist in the {banner text}. Everything contained between the first and second {char} characters, including carriage returns, is interpreted as the banner message. For example,

config t
banner motd #
******************************************
* Unauthorized access prohibited
******************************************
#

Courtesy http://www.tech-recipes.com/rx/83/add-a-login-banner-to-your-cisco-router/