Cisco WS-C2980G-A Software Guide - Page 341
Using Secure Shell Encryption for Telnet Sessions
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Chapter 20 Checking Status and Connectivity Using Secure Shell Encryption for Telnet Sessions This example shows how to set the logout timer value to 10 minutes: Console> (enable) set logout 10 Sessions will be automatically logged out after 10 minutes of idle time. Console> (enable) This example shows how to set the logout timer value to 0, preventing idle sessions from being disconnected automatically: Console> (enable) set logout 0 Sessions will not be automatically logged out. Console> (enable) Using Secure Shell Encryption for Telnet Sessions Note To use the secure shell encryption (SSH) feature commands, you must be running an encryption image. Encryption commands are set crypto key rsa, clear crypto key rsa, and show crypto key. See Chapter 33, "Working with System Software Images," for the software image naming conventions that are used for the encryption images. The SSH feature provides security for Telnet sessions to the switch. SSH is supported for remote logins to the switch only. Telnet sessions that are initiated from the switch cannot be encrypted. To use this feature, you must install the application on the client accessing the switch and you must configure SSH the switch. The current implementation of SSH supports version 1, both the data encryption standard (DES) and 3DES encryption methods, and can be used with RADIUS and TACACS+ authentication. To support authentication for Telnet with secure shell encryption, enter the telnet keyword in the set authentication commands. Note If you are using Kerberos to authenticate to the switch, you will not be able to use the secure shell encryption feature. To enable SSH on the switch, perform this task in privileged mode: Task Create the RSA host key. Command set crypto key rsa nbits [force] This example shows how to create the RSA host key: Console> (enable) set crypto key rsa 1024 Generating RSA keys.... [OK] Console> (enable) The nbits value specifies the RSA key size; the valid key size range is from 512 to 2048 bits. A key size with a larger number provides higher security but takes longer to generate. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 20-7
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