Configuring Secure Shell (SSH)

Configuring the Switch for SSH Operation

 

hosts file, note that the formatting and comments need not match. For version

 

1 keys, the three numeric values bit size, exponent <e>, and modulus <n> must

 

match; for PEM keys, only the PEM-encoded string itself must match.

 

 

N o t e s

"Zeroizing" the switch’s key automatically disables SSH (sets ip ssh to no).

 

Thus, if you zeroize the key and then generate a new key, you must also re-

 

enable SSH with the ip ssh command before the switch can resume SSH

 

operation.

 

 

Configuring Key Lengths

The crypto key generate ssh command allows you to specify the type and length of the generated host key. The size of the host key is platform-dependent as different switches have different amounts of processing power. The size is represented by the <keysize> parameter and has the values shown in Table 7-2. The default value is used if keysize is not specified.

Table 7-2. RSA/DSA Values for Various ProCurve Switches

Platform

Maximum RSA Key Size (in bits)

DSA Key Size (in bits)

5400/3500/6200/8200/2910

1024, 2048, 3072

1024

 

Default: 2048

 

4200/2900/2810/2610/2510

1024, 2048

1024

 

Default: 2048

 

5300/2800/3400/2600

896

512

 

 

 

3. Providing the Switch’s Public Key to Clients

When an SSH client contacts the switch for the first time, the client will challenge the connection unless you have already copied the key into the client’s "known host" file. Copying the switch’s key in this way reduces the chance that an unauthorized device can pose as the switch to learn your access passwords. The most secure way to acquire the switch’s public key for distribution to clients is to use a direct, serial connection between the switch and a management device (laptop, PC, or UNIX workstation), as described below.

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