Cisco Asa Generate Crypto Key

Posted on 24-05-2021 by admin

Asa Generate Crypto Key
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May 20, 2014 Author, teacher, and talk show host Robert McMillen shows you how to use the Cisco ASA version 9 generate RSA keys command. Cisco ASA Anyconnect Self Signed Certificate By default the Cisco ASA firewall has a self signed certificate that is regenerated every time you reboot it. This can be an issue when you are using SSL VPN as the web browser of your user will give a warning every time it sees an untrusted certificate. Run show crypto key mypubkey rsa to see if you do, in fact, have a key fully generated and registered under a non-default name. If there is, then you can tell the ssh process to use this key with ip ssh rsa keypair-name xxx. If the first command doesn't show anything useful then I'd say you can go ahead and generate a new key.

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.

Asa Generate Crypto Key

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

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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

Cisco Asa Crypto Key Generate Rsa

Send > Wait a couple of minutes and try again.

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