Technical data

BLADE OS 5.1 Application Guide
BMD00136, November 2009 Chapter 1: Accessing the Switch
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Generating RSA Host and Server Keys for SSH Access
To support the SSH server feature, two sets of RSA keys (host and server keys) are required. The
host key is 1024 bits and is used to identify the G8000. The server key is 768 bits and is used to
make it impossible to decipher a captured session by breaking into the G8000 at a later time.
When the SSH server is first enabled and applied, the switch automatically generates the RSA host
and server keys and is stored in the Flash memory. To configure RSA host and server keys, enter the
following commands to generate them manually.
When the switch reboots, it will retrieve the host and server keys from the Flash memory.
If these two keys are not available in the flash and if the SSH server feature is enabled, the switch
automatically generates them during the system reboot. This process may take several minutes to
complete.
The switch can automatically regenerate the RSA server key. To set the interval of RSA server key
autogeneration, use the following command:
A value of 0 (zero) denotes that RSA server key autogeneration is disabled. When greater
than 0, the switch will autogenerate the RSA server key every specified interval; however, RSA
server key generation is skipped if the switch is busy doing other key or cipher generation when the
timer expires.
Note – The switch will perform only one session of key/cipher generation at a time. Thus, an SSH
client will not be able to log in if the switch is performing key generation at that time, or if another
client has logged in immediately prior. Also, key generation will fail if an SSH client is logging in
at that time.
SSH Integration with RADIUS/TACACS+ Authentication
SSH is integrated with RADIUS authentication. After the RADIUS server is enabled on the switch,
all subsequent SSH authentication requests will be redirected to the specified RADIUS servers for
authentication. The redirection is transparent to the SSH clients.
SSH is integrated with TACACS+ authentication. After the TACACS+ server is enabled on the
switch, all subsequent SSH authentication requests will be redirected to the specified TACACS+
servers for authentication. The redirection is transparent to the SSH clients.
RS G8000 (config)# ssh generate-host-key
RS G8000 (config)# ssh generate-server-key
RS G8000 (config)# ssh interval <number of hours (0-24)>