Cisco 2501 - Router - EN Bedienungsanleitung PDF herunterladen (Seite 29)

Router and Switch Administrative Configurations

207

So what will happen if you try to telnet into a router that doesn’t have a VTY password set?

You’ll receive an error stating that the connection is refused because, well, the password isn’t

set. So, if you telnet into a router and receive the message

Todd#telnet SFRouter

Trying SFRouter (10.0.0.1)…Open

Password required, but none set

[Connection to SFRouter closed by foreign host]

Todd#

then the remote router (SFRouter in this example) does not have the VTY (Telnet) password set.

But you can get around this and tell the router to allow Telnet connections without a password

by using the no login command:

SFRouter(config-line)#line vty 0 4

SFRouter(config-line)#no login

I do not recommend using the no login command to allow Telnet connections

without a password unless you are in a testing or classroom environment! In a

production network, you should always set your VTY password.

After your routers are configured with an IP address, you can use the Telnet program to con-

figure and check your routers instead of having to use a console cable. You can use the Telnet pro-

gram by typing telnet from any command prompt (DOS or Cisco). Anything Telnet is covered

more thoroughly in Chapter 5.

Setting Up Secure Shell (SSH)

Instead of Telnet, you can use Secure Shell, which creates a more secure session than the Telnet

application that uses an unencrypted data stream. Secure Shell (SSH) uses encrypted keys to

send data so that your username and password are not sent in the clear.

I recommend using SSH instead of Telnet whenever possible.

Here are the steps for setting up SSH:

1. Set your hostname:

Router(config)#hostname Todd

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Cisco 2501 - Router - EN Bedienungsanleitung Seite 29