Technical data

6 ServerIron ADX Administration Guide

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Configuring SSH

The ServerIron ADX supports up to five concurrent inbound Telnet and SSH sessions, one outbound

Telnet session, and console access. Write access through Telnet and SSH is limited to one session

only.

NOTE

SSH public key authentication supports only DSA keys. RSA keys are not supported.

Enabling or disabling SSH service

The SSH service is not enabled by default. The SSH server starts once you configure a host DSA

public and private key pair for SSH.

ServerIronADX(config)# crypto key generate dsa

ServerIronADX(config)# write mem

Syntax: [no] crypto key generate dsa

The host DSA key pair is stored in the system-config file. Only the public key is readable. The host

DSA key pair is used to negotiate a session key and encryption method with the SSH clients trying

to connect to the ServerIron ADX.

The service is stopped once the keys are destroyed from the system-config file.

ServerIronADX(config)# crypto key zeroize dsa

ServerIronADX(config)# write mem

Syntax: crypto key zeroize dsa

There is no SSH client within the ServerIronADX to support outbound sessions initiated from within

the ServerIronADX.

At a minimum, the following SSH clients are supported for inbound connections:

• F-Secure 5.3

• Secure Shell 3.2.3

• SecureCRT 4.0

• PuTTY 0.54

• Tera Term Pro 3.1.3

• OpenSSH_3.5p1

Creating a seed for generating a random number

To create a new seed for generating a random number that is used for generating the dynamically

created server DSA key pair for SSH, enter the following command.

ServerIronADX(config)# crypto random-number-seed generate

Syntax: [no] crypto random-number-seed

Setting SSH authentication retries

To set the number of SSH authentication retries, enter the following command.