1. Crypto Key Generate Rsa Modulus 1024 Asa 2
2. Crypto Key Generate Rsa Modulus 1024 Asa 2017
3. Crypto Key Generate Rsa 1024
4. Cisco Crypto Key Generate Rsa
5. Generate A Rsa Crypto Key

KB ID 0001322

Problem

Sep 09, 2010  ASA5505: Setting up ssh for remote management. By Cyrus Lok on Thursday, April 8, 2010 at 11:13pm I have a generated RSA key which is stored in my ASA's flash memory. I am going to recreate a RSA key once more, so I will zeroize the key. If there is a RSA key stored in. Crypto key generate rsa general-keys label tokenkey1 storage usbtoken0: The following example specifies the redundancy keyword: Router(config)# crypto key generate rsa label MYKEYS redundancy. The name for the keys will be: MYKEYS Choose the size of the key modulus in the range of 360 to 2048 for your General Purpose Keys.

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

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

• October 2, 2015
• Posted by: Syed Shujaat
• Category: Cisco, Networking Solutions

Use this command to generate RSA key pairs for your Cisco device (such as a router). keys are generated in pairs–one public RSA key and one private RSA key.

If your router already has RSA keys when you issue this command, you will be warned and prompted to replace the existing keys with new keys.

NOTE: Before issuing this command, ensure that your router has a hostname and IP domain name configured (with the hostname and ipdomain-name commands).

You will be unable to complete the cryptokeygeneratersacommand without a hostname and IP domain name. (This situation is not true when you generate only a named key pair.)

Here are the steps to Enable SSH and Crypto Key setup : 2 config must requried for SSH

Crypto Key Generate Rsa Modulus 1024 Asa 2

1 Setup Local VTY line User ID and password

router (Config) # Line VTY 0 15

router (Config-line)# login local

router (Config-line)# Exit

!!! create local login ID/Pass

router (Config)# username [loginid] password [cisco]

Crypto Key Generate Rsa Modulus 1024 Asa 2017

router (Config)# username loginid1 password cisco1

Crypto Key Generate Rsa 1024

2. router (Config)# ip domain-name example.com

router (Config)# crypto key generate rsa

how many bits in the modulus [512] :1024

router (Config)# ip ssh version2

router (Config)# CTRL Z

This command is not saved in the router configuration; however, the RSA keys generated by this command are saved in the private configuration in NVRAM (which is never displayed to the user or backed up to another device) the next time the configuration is written to NVRAM.

Cisco Crypto Key Generate Rsa

Modulus Length

When you generate RSA keys, you will be prompted to enter a modulus length. The longer the modulus, the stronger the security. However, a longer modules take longer to generate (see the table below for sample times) and takes longer to use.

The size of Key Modulus range from 360 to 2048. Choosing modulus greater than 512 will take longer time.

Cisco IOS software does not support a modulus greater than 4096 bits. A length of less than 512 bits is normally not recommended. In certain situations, the shorter modulus may not function properly with IKE, so we recommend using a minimum modulus of 2048 bits.

Syntax Description : Optional Strings to embed with SSH Crypto key

Generate A Rsa Crypto Key