stored on the switch can access it. The following exchanges take place during
this process:
Authenticating SSH v1.5 Clients
a. The client sends its RSA public key to the switch.
b. The switch compares the client's public key to those st ored in memo ry.
c. If a match is found, the switch uses its secret key to gene rate a random
256-bit string as a challenge, encrypts this string with the user’s p ublic key,
and sends it to the client.
d. The client uses its private key to dec rypt the cha llenge string , compute s the
MD5 checksum, and sends the checksum back to the switch.
e. The switch compares the checksum sent from the client against th at
computed for the original string it sent. If the two checksums match, this
means that the client's private key corresponds to an authorized public key,
and the client is authenticated.
Authenticating SSH v2 Clients
a. The client first queries the switch to determ ine if DSA publ ic key
authentication using a preferred algorithm is acceptable.
b. If the specified algorithm is supported by the swit ch, it notif ies the clien t to
proceed with the authentication process. Otherwise, it rej ects t he req uest.
c. The client sends a si gnatur e generated using the p rivate ke y to the swi tch.
d. When the serv er recei ves this mes sage, it che cks whet her the suppl ied ke y
is acceptable for authentication, and if so, it then checks whether the
signature is correct. If both checks succeed, the client is authenticated.
Note:
The SSH server supports up to four client sessions. The maximum number of
client sessions includes both current Telnet sessions and SSH sessions.
ip ssh server
This command enables the Secure Shell (SSH) server on this switch. Use the
no
form to disable this service.
Syntax
[no] ip ssh server
Default Setting
Disabled
Command Mode
Global Configuration
Command Usage
• The SSH server supports up to four client sessions. The maximum number of
client sessions includes both current Telnet sessions and SSH sessions.
• The SSH server uses DSA or RSA for key exchange when t he client fir st
establishes a connection with the switch, and then negotiates with th e client
to select either DES (56-bit) or 3DES (168-bit) for data encryption.
• You mu st g en erat e D SA an d RSA host keys before enabling the SSH ser ve r.
25-17Secure She l
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