in Cisco, How To's, Networking

How To: Enable SSH On A Cisco 2950

First you have to make sure you are running a version of code that has encryption. See my previous article for instructions on how to upgrade the code. Once your code is upgraded, here are the steps to enable SSH on a Cisco 2950.

Generate An SSH Key

switch-2950-1.tuxlabs.com#config t
Enter configuration commands, one per line.  End with CNTL/Z.
switch-2950-1.tuxlabs(config)#crypto key generate rsa modulus 1024
The name for the keys will be: switch-2950-1.tuxlabs.com.tuxlabs.com

% The key modulus size is 1024 bits
Generating RSA keys ...
[OK]

switch-2950-1.tuxlabs(config)#exit
switch-2950-1.tuxlabs.com#

Verify your key like so

switch-2950-1.tuxlabs.com#show crypto key mypubkey rsa 
% Key pair was generated at: 00:10:35 UTC Mar 1 1993
Key name: switch-2950-1.tuxlabs.com.tuxlabs.com
 Usage: General Purpose Key
 Key Data:
  30819F30 0D06092A 864886F7 0D010101 05000381 8D003081 89028181 00E6AA25 
  8DB58145 F882CD0B C62F5123 AB0064A6 A09BD636 FA854D82 B1510A31 3A00606E 
  00F601F1 ECF64FCC 0F516E73 E80E0961 9CCCE91B 5C3D5919 4803B805 04AC2633 
  9D0A32E8 0196F572 5CE9FFF4 A5C27FC4 698DE75B F0573804 22D0CCFE 58936F4E 
  5BE394F4 3BDED1AC DC1BF1C9 5E71ABD5 34F1C21E CDA47B7E 72D40C34 6B020301 0001
% Key pair was generated at: 00:10:41 UTC Mar 1 1993
Key name: switch-2950-1.tuxlabs.com.tuxlabs.com.server
 Usage: Encryption Key
 Key Data:
  307C300D 06092A86 4886F70D 01010105 00036B00 30680261 009F3354 2ECB6FB6 
  7A19D04D 929FEB38 05145D39 C9DB6CAB 5AC1A262 14FEFFBC DE6E5FA9 8565BEA6 
  1A888A92 C7D1ED2E DB8D3894 D972C9AE 853DFB98 8261D518 0F8A994C 9293C49C 
  0E946A95 0F89EA08 45E4DCB7 74F5A23C CDC5938C CD01C6C1 4D020301 0001
switch-2950-1.tuxlabs.com#

Wow 1993, feels good to be a time machine 🙂

Configure the allowed number of retries

switch-2950-1.tuxlabs.com#config t                     
Enter configuration commands, one per line.  End with CNTL/Z.
switch-2950-1.tuxlabs(config)#ip ssh authentication-retries 5
switch-2950-1.tuxlabs(config)#exit
switch-2950-1.tuxlabs.com#

Enabling SSH on the VTYs

switch-2950-1.tuxlabs.com#config t           
Enter configuration commands, one per line.  End with CNTL/Z.
switch-2950-1.tuxlabs(config)#line vty 0 4
switch-2950-1.tu(config-line)#login local
switch-2950-1.tu(config-line)#transport input ssh
switch-2950-1.tu(config-line)#line vty 5 15
switch-2950-1.tu(config-line)#login local
switch-2950-1.tu(config-line)#transport input ssh
switch-2950-1.tu(config-line)#exit
switch-2950-1.tuxlabs(config)#exit
switch-2950-1.tuxlabs.com#wr mem
Building configuration...
[OK]
switch-2950-1.tuxlabs.com#

Configuring A Username

When you’re running telnet you don’t need a username. But when you are using SSH, you do.

switch-2950-1.tuxlabs.com#config t 
Enter configuration commands, one per line.  End with CNTL/Z.
switch-2950-1.tuxlabs(config)#username tuxninja privilege 15 password sup3rs3cr3t
switch-2950-1.tuxlabs(config)#exit
switch-2950-1.tuxlabs.com#wr mem
Building configuration...
[OK]
switch-2950-1.tuxlabs.com#

Now were golden, let’s test.

➜  ~  ssh tuxninja@switch-2950-1.tuxlabs.com
The authenticity of host 'switch-2950-1.tuxlabs.com (192.168.1.2)' can't be established.
RSA key fingerprint is 21:6b:44:bb:24:ff:ef:14:9d:f2:00:44:64:3d:3b:f8.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'switch-2950-1.tuxlabs.com,192.168.1.2' (RSA) to the list of known hosts.
tuxninja@switch-2950-1.tuxlabs.com's password: 

switch-2950-1.tuxlabs.com#show privil
switch-2950-1.tuxlabs.com#show privilege 
Current privilege level is 15
switch-2950-1.tuxlabs.com#exit
Connection to switch-2950-1.tuxlabs.com closed.
➜  ~

Awesome ! That concludes this short tutorial.

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