Previously, I wrote about how you can enable SSH access to your Cisco switch by enabling the setting in the GUI interface. This is great if you want to access your switch CLI over an encrypted connection, but it still relies on just a username and password.
Generate Rsa Keys Cisco Switch For Windows 10
Solved: I have a Cisco 1811W running 12.4(6)T2 (c181x-advipservicesk9-mz.124-6.T2.bin), and I'm wanting to turn off telnet access to it and turn on SSH which I usually do on all the routers I manage, but on this particular router when I put in the. Crypto key generate rsa - crypto key generate rsa general-keys modulus 2048 - crypto key generate rsa general-keys label SSH modulus 2048. None of the above worked.and the SSH key remains 1024. Does anyone know how to change the SSH Key for this switch from 1024 to 2048? Version is Version 12.2(50)SE4. Statements included in the config file listed below and then I pasted these statements onto the switch, would that cause the rsa key to get rejected? I did a little research and found out that if I removed the rsa key by using this command ' crypto key zeroize rsa' and then added the ' crypto key generate rsa generate - keys modulus 1024, then. Oct 16, 2019 When you generate RSA key pairs (via the crypto key generate rsa command), you will be prompted to select either usage keys or general-purpose keys. Usage RSA Keys Usage keys consist of two RSA key pairs-one RSA key pair is generated and used for encryption and one RSA key pair is generated and used for signatures.
If you are using this switch in a highly sensitive network that needs to be very secure, then you might want to consider enabling public key authentication for your SSH connection. Actually, for maximum security, you can enable a username/password and public key authentication for access to your switch.
In this article, I’ll show you how to enable public key authentication on an SG300 Cisco switch and how to generate the public and private key pairs using puTTYGen. I’ll then show you how to login using the new keys. In addition, I’ll show you how to configure it so that you can either use just the key to login or force the user to type in a username/password along with using the private key.
Note: Before you get started on this tutorial, make sure you have already enabled the SSH service on the switch, which I mentioned in my previous article linked above.
Enable SSH User Authentication by Public Key
Overall, the process for getting public key authentication to work for SSH is straightforward. In my example, I’ll show you how to enable the features using the web-based GUI. I tried to use the CLI interface to enable public key authentication, but it would not accept the format for my private RSA key.
Once I get that working, I’ll update this post with the CLI commands that will accomplish what we will do through the GUI for now. First, click on Security, then SSH Server and finally SSH User Authentication.
In the right-hand pane, go ahead and check the Enable box next to SSH User Authentication by Public Key. Click the Apply button to save the changes. Don’t check the Enable button next to Automatic login just yet as I’ll explain that further down.
Now we have to add a SSH user name. Before we get into adding the user, we first have to generate a public and private key. In this example, we’ll be using puTTYGen, which is a program that comes with puTTY.
Generate Private and Public Keys
To generate the keys, go ahead and open puTTYGen first. You’ll see a blank screen and you really shouldn’t have to change any of the settings from the defaults shown below.
Click on the Generate button and then move your mouse around the blank area until the progress bar go all the way across.
Once the keys have been generated, you need to type in a passphrase, which is basically like a password to unlock the key.
It’s a good idea to use a long passphrase to protect the key from brute-force attacks. Once you have typed in the passphrase twice, you should click the Save public key and Save private key buttons. Make sure these files are saved in a secure location, preferably in an encrypted container of some sort that requires a password to open. Check out my post on using VeraCrypt to create an encrypted volume.
Add User & Key
Now back to the SSH User Authentication screen we were on earlier. Here’s where you can choose from two different options. Firstly, go to Administration – User Accounts to see what accounts you currently have for login.
As you can see, I have one account called akishore for accessing my switch. Currently, I can use this account to access the web-based GUI and the CLI. Back on the SSH User Authentication page, the user you need to add to the SSH User Authentication Table (by Public Key) can either be the same as what you have under Administration – User Accounts or different.
If you choose the same user name, then you can check the Enable button under Automatic Login and when you go to log into the switch, you’ll simply have to type the username and password for the private key and you’ll be logged in.
If you decide to choose a different username here, then you will get a prompt where you have to enter the SSH private key user name and password and then you’ll have to enter your normal username and password (listed under Admin – User Accounts). If you want the extra security, use a different username, otherwise just name it the same as your current one.
Click the Add button and you’ll get the Add SSH User window pop up.
Make sure the Key Type is set to RSA and then go ahead and open your public SSH key file that you saved earlier using a program like Notepad. Copy the entire contents and paste it into the Public Key window. Click Apply and then click Close if you get a Success message at the top.
Login Using Private Key
Now all we have to do is login using our private key and password. At this point, when you try to login, you’ll need to enter login credentials twice: once for the private key and once for the normal user account. Once we enable automatic login, you’ll just have to enter the username and password for the private key and you’ll be in.
Open puTTY and enter in the IP address of your switch in the Host Name box as usual. However, this time, we’ll need to load up the private key into puTTY also. To do this, expand Connection, then expand SSH and then click on Auth.
Click on the Browse button under Private key file for authentication and select the private key file you saved out of puTTY earlier. Now click the Open button to connect.
The first prompt will be login as and that should be the username you added under SSH users. If you used the same username as your main user account, then it won’t matter.
In my case, I used akishore for both user accounts, but I used different passwords for the private key and for my main user account. If you like, you can make the passwords the same too, but there’s no point in really doing that, especially if you enable automatic login.
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Now if you don’t want to have to double login to get into the switch, check the Enable box next to Automatic login on the SSH User Authentication page.
When this is enabled, you’ll now just have to type in the credentials for the SSH user and you’ll be logged in.
It’s a bit complicated, but makes sense once you play around with it. Like I mentioned earlier, I’ll also write out the CLI commands once I can get the private key in the proper format. Following the instructions here, accessing your switch via SSH should be a lot more secure now. If you run into problems or have questions, post in the comments. Enjoy!
Cpsc 370 aes key generator. November 18, 2010.
ContentsIntroduction
Secure Shell (SSH) is a protocol which provides a secure remote access connection to network devices. Communication between the client and server is encrypted in both SSH version 1 and SSH version 2. Implement SSH version 2 when possible because it uses a more enhanced security encryption algorithm.
This document discusses how to configure and debug SSH on Cisco routers or switches that run a version of Cisco IOS® Software that supports SSH. This document contains more information on specific versions and software images.
PrerequisitesRequirements
The Cisco IOS image used must be a k9(crypto) image in order to support SSH. For example c3750e-universalk9-tar.122-35.SE5.tar is a k9 (crypto) image.
Components Used
The information in this document is based on Cisco IOS 3600 Software (C3640-IK9S-M), Release 12.2(2)T1.
SSH was introduced into these Cisco IOS platforms and images:
Refer to the Software Advisor (registered customers only) for a complete list of feature sets supported in different Cisco IOS Software releases and on different platforms.
The information presented in this document was created from devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If you are in a live network, make sure that you understand the potential impact of any command before you use it.
Conventions
Refer to Cisco Technical Tips Conventions for more information on document conventions.
SSH v1 vs. SSH v2
Use the Cisco Software Advisor (registered customers only) in order to help you find the version of code with appropriate support for either SSH v1 or SSH v2.
Network DiagramTest AuthenticationAuthentication Test without SSH
First test the authentication without SSH to make sure that authentication works with the router Carter before you add SSH. Authentication can be with a local username and password or with an authentication, authorization, and accounting (AAA) server that runs TACACS+ or RADIUS. (Authentication through the line password is not possible with SSH.) This example shows local authentication, which lets you Telnet into the router with username 'cisco' and password 'cisco.'
Authentication Test with SSH
In order to test authentication with SSH, you have to add to the previous statements in order to enable SSH on Carter and test SSH from the PC and UNIX stations.
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. If this does not work, see the debug section of this document.
Optional Configuration SettingsPrevent Non-SSH Connections
If you want to prevent non-SSH connections, add the transport input ssh command under the lines to limit the router to SSH connections only. Straight (non-SSH) Telnets are refused.
Generate Rsa Key Cisco Switch
Test to make sure that non-SSH users cannot Telnet to the router Carter.
Set Up an IOS Router or Switch as SSH Client
There are four steps required to enable SSH support on a Cisco IOS router:
If you want to have one device act as an SSH client to the other, you can add SSH to a second device called Reed. These devices are then in a client-server arrangement, where Carter acts as the server, and Reed acts as the client. The Cisco IOS SSH client configuration on Reed is the same as required for the SSH server configuration on Carter.
Issue this command to SSH from the Cisco IOS SSH client (Reed) to the Cisco IOS SSH server (Carter) in order to test this:
Setup an IOS Router as an SSH server that performs RSA based User Authentication
Complete these steps in order to configure the SSH server to perform RSA based authentication.
Add SSH Terminal-Line Access
If you need outbound SSH terminal-line authentication, you can configure and test SSH for outbound reverse Telnets through Carter, which acts as a comm server to Philly.
If Philly is attached to Carter's port 2, then you can configure SSH to Philly through Carter from Reed with the help of this command:
You can use this command from Solaris:
Restrict SSH access to a subnet
You need to limit SSH connectivity to a specific subnetwork where all other SSH attempts from IPs outside the subnetwork should be dropped.
You can use these steps to accomplish the same:
This is an example configuration. In this example only SSH access to the 10.10.10.0 255.255.255.0 subnet is permitted, any other is denied access.
Note: The same procedure to lock down the SSH access is also applicable on switch platforms.
Configure the SSH Version
Configure SSH v1:
Configure SSH v2:
Configure SSH v1 and v2:
Note: You receive this error message when you use SSHv1:
Note: Cisco bug ID CSCsu51740 (registered customers only) is filed for this issue. Workaround is to configure SSHv2.
Variations on banner Command Output
The banner command output varies between the Telnet and different versions of SSH connections. This table illustrates how different banner command options work with various types of connections.
Unable to Display the Login Banner
SSH version 2 supports the login banner. The login banner is displayed if the SSH client sends the username when it initiates the SSH session with the Cisco router. For example, when the Secure Shell ssh client is used, the login banner is displayed. When the PuTTY ssh client is used, the login banner is not displayed. This is because Secure Shell sends the username by default and PuTTY does not send the username by default.
The Secure Shell client needs the username to initiate the connection to the SSH enabled device. The Connect button is not enabled if you do not enter the host name and username. This screenshot shows that the login banner is displayed when Secure Shell connects to the router. Then, the login banner password prompt displays.
The PuTTY client does not require the username to initiate the SSH connection to the router. This screenshot shows that the PuTTY client connects to the router and prompts for the username and password. It does not display the login banner.
This screen shot shows that the login banner is displayed when PuTTY is configured to send the username to the router.
debug and show Commands
Before you issue the debug commands described and illustrated here, refer to Important Information on Debug Commands. Certain show commands are supported by the Output Interpreter Tool (registered customers only) , which allows you to view an analysis of show command output.
Sample Debug OutputRouter Debug
Note: Some of this good debug output is wrapped to multiple lines because of spatial considerations.
Server Debug
Note: This output was captured on a Solaris machine.
What can go Wrong
These sections have sample debug output from several incorrect configurations.
SSH From an SSH Client Not Compiled with Data Encryption Standard (DES)Solaris DebugRouter DebugBad PasswordRouter DebugSSH Client Sends Unsupported (Blowfish) CipherRouter DebugGeting the '%SSH-3-PRIVATEKEY: Unable to retrieve RSA private key for' Error
If you receive this error message, it may be caused due to any change in the domain name or host name. In order to resolve this, try these workarounds.
Cisco bug ID CSCsa83601 (registered customers only) has been filed to address this behaviour.
Troubleshooting Tips
Related InformationComments are closed.
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