3com 5500-SI Manual De Usuario

SSH Terminal Services 507

way: The RSA public key of the client user is configured at the server. The client 
first sends the member modules of its RSA public key to the server, which checks 
its validity. If it is valid, the server generates a random number, which is sent to the 
client after being encrypted with RSA public key. Both ends calculate 
authentication data based on the random number and session ID. The client sends 
the authentication data calculated back to the server, which compares it with its 
attention data obtained locally. If they match exactly, the user is allowed to access 
the Switch. Otherwise, authentication process fails.

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Session request stage: The client sends session request messages to the server 
which processes the request messages. 

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Interactive session stage: Both ends exchange data till the session ends. 

Session packets are encrypted in transfer and the session key is generated 
randomly. Encryption is used in exchanging session key and RSA authentication 
achieves key exchange without transfer over the network. SSH can protect 
server-client data security. The authentication will also start even if the username 
received is not configured at the server, so malicious intruders cannot judge 
whether a username they key in exists or not. This is also a way to protect a 
username. 

Basic configuration tasks refer to those required for successful connection from SSH 
client to SSH server, which advanced configuration tasks are those modifying SSH 
parameters. 

Configuration tasks on the SSH server include: 

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Setting system protocol and link maximum

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Configuring and deleting local RSA key pair

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Configuring authentication type

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Defining update interval of server key

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Defining SSH authentication timeout value

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Defining SSH authentication retry value

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Entering public key view and editing public key

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Associating public key with SSH user

You must specify SSH protocol for the system before enabling SSH. 

Perform the following configuration in System View.

Table 577   Setting System Protocols and Link Maximum

By default, the system supports Telnet and SSH protocols.

Set system protocol and link maximum protocol inbound { all | ssh | telnet }