Chapter23 Router Properties
VTYs
23-20
Cisco Router and Security Device Manager Version 2.2 User’s Guide
OL-4015-08
SSH
This router implements Secure Shell (SSH) Server, a feature that enables an SSH
client to make a secure, encrypted connection to a Cisco router. This connection
provides functionality that is similar to that of an inbound Telnet connection, but
that provides strong encryption to be used with Cisco IOS software
authentication. The SSH server in Cisco IOS software will work with publicly and
commercially available S SH client s. This feature is disabled if the router is not using
an IPSEC DES or 3DES Cisco IOS software image, and if the SSH branch of the
Additional Tasks tree does not appear.
SSH uses an RSA crypto key to encrypt data traveling between the router and the
SSH client. Generating the RSA key in this window enables SSH communication
between the router and the SSH clients.

Status

Crypto key is not set on this device
This text appears if there is no crypto key configured for the device. If there is no
key configured, you can enter a modulus size, and generate a key.
RSA key is set on this router
This text appear if a crypto key has been generate. SSH is enab led on this router.

Key modulus size

This button is visible if no crypto key has been generated. Click thi s button and
enter the modulus size you want to give the key. If you want a modulus value
between 512 and 1024 enter an integer value that is a multiple of 64. If you want
a value higher than 1024, you can enter 1536 or 2048. If you enter a value greater
than 512, key generation may take a minute or longer.

Generate RSA Key

Click this button to generate a crypto key for the router using the modulus size
you entered. If the crypto key has already been generated, this button is disabled.