System information

98 Chapter 3: Defending the Perimeter

Creating a Banner Message

When someone connects to one of your routers, he sees some sort of message or prompt.

For legal reasons, Cisco suggests that a banner message be displayed to warn potential

attackers not to attempt a login. For example, you wouldn’t want to use a banner message

that says, “Welcome! You are connected to Router 1.” An attacker could use such a message

as part of his legal defense, stating that he was told that he was welcomed to your router.

Please consult competent legal counsel when phrasing the banner message. However, as

soon as you have the appropriate verbiage for your banner message, you can apply the

message to your router with the banner motd delimiter message_body delimiter command.

The motd parameter stands for “message of the day,” and the delimiter is a character you

choose to indicate the beginning and end of the banner message. Therefore, you should

choose a delimiter that will not appear in the message body. Example 3-18 shows how to

create a banner message. Notice that the $ character is used as the delimiter. Example 3-19

shows the new banner message presented to a user who just connected to the router via

Telnet.

Example 3-17 Conﬁguring Enhanced Support for Virtual Logins

R1# cc

R1(config)# ll

R1(config)# ee

R1# ss

A login delay of 3 seconds is applied.

Quiet-Mode access list 101 is applied.

All successful login is logged.

All failed login is logged.

Router enabled to watch for login Attacks.

If more than 5 login failures occur in 10 seconds or less,

logins will be disabled for 30 seconds.

Router presently in Normal-Mode.

Current Watch Window

Time remaining: 9 seconds.

Total login failures: 0.

R1#