Cisco Asa Ssh Crypto Key Generate
- 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
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. Besides allowing the permitted hosts to SSH to the ASA, you need to define RSA keys for the secure connection. In the CLI: crypto key generate rsa. For these key to work, you should have a hostname/domain-name configured on the ASA as well (unless you configure a dedicated RSA keys).
1 Setup Local VTY line User ID and password
- Oct 14, 2008 This document provides a sample configuration of Secure Shell (SSH) on the inside and outside interfaces of Cisco Series Security Appliance version 7.x and later. The configuration of the Series Security Appliance remotely with the command line involves the use of either Telnet or SSH.
- 2 hours ago Ip domain-name rtp.cisco.com!- Generate an SSH key to be used with SSH. Crypto key generate rsa ip ssh time-out 60 ip ssh authentication-retries 2. At this point, the show crypto key mypubkey rsa command must show the generated key. After you add the SSH configuration, test your ability to access the router from the PC and UNIX station.
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]
router (Config)# username loginid1 password cisco1
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
Note | Secure Shell (SSH) may generate an additional RSA key pair if you generate a key pair on a router having no RSA keys. The additional key pair is used only by SSH and will have a name such as {router_FQDN }.server. For example, if a router name is “router1.cisco.com,” the key name is “router1.cisco.com.server.” |
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.
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. Office product key generator 2007. Choosing modulus greater than 512 will take longer time.
| Router | 360 bits | 512 bits | 1024 bits | 2048 bits (maximum) |
|---|---|---|---|---|
| Cisco 2500 | 11 seconds | 20 seconds | 4 minutes, 38 seconds | More than 1 hour |
| Cisco 4700 | Less than 1 second | 1 second | 4 seconds | 50 seconds |
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
| general-keys | (Optional) Specifies that a general-purpose key pair will be generated, which is the default. | ||
| usage-keys | (Optional) Specifies that two RSA special-usage key pairs, one encryption pair and one signature pair, will be generated. | ||
| signature | (Optional) Specifies that the RSA public key generated will be a signature special usage key. | ||
| encryption | (Optional) Specifies that the RSA public key generated will be an encryption special usage key. | ||
| labelkey-label | (Optional) Specifies the name that is used for an RSA key pair when they are being exported.If a key label is not specified, the fully qualified domain name (FQDN) of the router is used. | ||
| exportable | (Optional) Specifies that the RSA key pair can be exported to another Cisco device, such as a router. | ||
| modulusmodulus-size | (Optional) Specifies the IP size of the key modulus.By default, the modulus of a certification authority (CA) key is 1024 bits. The recommended modulus for a CA key is 2048 bits. The range of a CA key modulus is from 350 to 4096 bits.
| ||
| storagedevicename: | (Optional) Specifies the key storage location. The name of the storage device is followed by a colon (:). | ||
| redundancy | (Optional) Specifies that the key should be synchronized to the standby CA. | ||
| ondevicename: | (Optional) Specifies that the RSA key pair will be created on the specified device, including a Universal Serial Bus (USB) token, local disk, or NVRAM. The name of the device is followed by a colon (:).Keys created on a USB token must be 2048 bits or less. |
| Command | Description |
|---|---|
| copy | Copies any file from a source to a destination, use the copy command in privileged EXEC mode. |
| cryptokeystorage | Sets the default storage location for RSA key pairs. |
| debugcryptoengine | Displays debug messages about crypto engines. |
| hostname | Specifies or modifies the hostname for the network server. |
| ipdomain-name | Defines a default domain name to complete unqualified hostnames (names without a dotted-decimal domain name). |
| showcryptokeymypubkeyrsa | Displays the RSA public keys of your router. |
| show crypto pki certificates | Displays information about your PKI certificate, certification authority, and any registration authority certificates. |
KB ID 0001322
Cisco Asa Crypto Key Generate Rsa Modulus 2048
Problem
Cisco Asa Ssh Crypto Key Generate Rsa Modulus 1024 Not Working In Packet Tracer
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.
Mac download link command line. REMEMBER: I’m assuming you have SSH setup correctly if not, see the following article;
Crypto Key Generate Rsa Command
Related Articles, References, Credits, or External Links
Cisco Asa Ssh Crypto Key Generate Key
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