Generating RSA Keys Problem You want to create a shareable RSA key for authentication or encryption. Solution First, you must create the keys on both devices. We recommend using at - Selection from Cisco IOS Cookbook, 2nd Edition Book.
  • Dec 26, 2013  so it looks as if there is no point in the 'crypto key generate rsa' command if i follow it up with the 'crypto key generate rsa usage-keys label sshkeys mod 1024' command, i just wanted to make sure the first wasn't need for the second to work or something screwy like that.
  • Router(config)# crypto key generate rsa usage-keys The name for the keys will be: myrouter.example.com Choose the size of the key modulus in the range of 360 to 2048 for your Signature Keys. Choosing a key modulus greater than 512 may take a few minutes.

KB ID 0001322

Problem

I’ve lost count of the number of times this has happened to me! Most of my colleagues prefer to use the ASDM for remote management, but if (like me) you work at command line, then sometimes people <ahem> forget to generate the RSA keypair when deploying a firewall. Then even if SSH access and AAA is setup correctly, you still can’t get in via SSH. Instead you see the following;

RoyalTS and RoyalTSX: ssh_exchange_identification: Connection closed by remote host.

PuTTY: PuTTY Fatal Error: Server unexpectedly closed network connection.

SecureCRT: Connection closed.

OSX/Linux: ssh_exchange_identification: Connection closed by remote host.

Now at command line you can fix this with a ‘Crypto Key Generate RSA Modulus 2048‘ command, but you can’t get to command line only ASDM.

Solution

On older versions of the ASDM you could generate the keypair in the Identification Certificates section (well you still can but only if you are also generating a certificate request file). So, as we are command line warriors, lets use the ASDM’s command line!

Tools > Command Line Interface > Multiple Line

Crypto Rsa Key Generate Cisco
Send > Wait a couple of minutes and try again.

REMEMBER: I’m assuming you have SSH setup correctly if not, see the following article;

Related Articles, References, Credits, or External Links

NA

Q: I have a Cisco switch in my network, which I can access by hooking up a console cable directly to the device. I like to access the switch remotely using SSH. How can I enable ssh on my Cisco 3750 Catalyst Switch?
A: By default, when you configure a Cisco device, you have to use the console cable and connect directly to the system to access it. Follow the steps mentioned below, which will enable SSH access to your Cisco devices. Once you enable SSH, you can access it remotely using PuTTY or any other SSH client.

1. Setup Management IP

First, make sure you have performed basic network configurations on your switch. For example, assign default gateway, assign management ip-address, etc. If this is already done, skip to the next step.
In the following example, the management ip address is set as 192.168.101.2 in the 101 VLAN. The default gateway points to the firewall, which is 192.168.101.1

2. Set hostname and domain-name

Next, make sure the switch has a hostname and domain-name set properly.

3. Generate the RSA Keys

Rsa
The switch or router should have RSA keys that it will use during the SSH process. So, generate these using crypto command as shown below.
Also, if you are running on an older Cisco IOS image, it is highly recommended that you upgrade to latest Cisco IOS.

4. Setup the Line VTY configurations

Setup the following line vty configuration parameters, where input transport is set to SSH. Set the login to local, and password to 7.
If you have not set the console line yet, set it to the following values.

5. Create the username password

If you don’t have an username created already, do it as shown below.
Note: If you don’t have the enable password setup properly, do it now.
Make sure the password-encryption service is turned-on, which will encrypt the password, and when you do “sh run”, you’ll seee only the encrypted password and not clear-text password.

5. Verify SSH access

From the switch, if you do ‘sh ip ssh’, it will confirm that the SSH is enabled on this cisco device.

Generate A Rsa Crypto Key

After the above configurations, login from a remote machine to verify that you can ssh to this cisco switch.
In this example, 192.168.101.2 is the management ip-address of the switch.
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Crypto Key Generate Rsa Cisco



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