The KEX algorithms are used to protect the key exchange process. Ip ssh server algorithm authentication keyboard Password, SecureID and hardware tokens, Pluggable Authentication Module (PAM) and S/KEY (and other One-Time-Pad)OTP. This allows for many different types of authentication including: We will be using keyboard authentication. ![]() SSH 1.99 is the default and is ‘compatibility mode’, that is version 1 and version 2 are supported. A common misconception is that version 1.99 is right and correct, however, SSH 1.99 is not SSH version 2. Ip ssh rsa keypair-name my-4096rsa-ssh-key !Ĭrypto key generate rsa modulus 4096 label my-4096rsa-ssh-key ![]() Modern (newer than 2016) IOS XE devices have more than enough CPU for a key length of 4096 and in order to maintain a similar level of security strength, we will need a key this long. In order to use SSH version 2, we need to create a key pair with at least 2048 bit key length. We will create a specific RSA key pair that is only used for SSH. IOS XE prior to 17.2 on other platforms will have varying levels of support as well. I have tested both C3750 and C3850 with the most current IOS XE and have had varying levels of support. This configuration will not fully work on C3750X and \ or C3850. We will do our best to match the strength of the public key exchange algorithm with the security strength of the symmetric cipher.Ĭat9K IOS XE 17.2(1) and later - Fully Supported This document will show you how to configure IOS XE to assure the cryptographic primers in use provide the highest level of security. It is desirable that the security strength of the key exchange be chosen to be comparable with the security strength of the other elements of the SSH handshake as attackers can target the weakest element of the SSH handshake. I will account for four (4) client programs Secure CRT, putty, the built-in OpenSSH client in Mac OSX 12, and the built-in SSH client in IOS XE. In this document, we shift the balance and provide security at the expense of compatibility. In the default configuration more of these are enabled than we would desire for a strong secure session this provides compatibility at the expense of security. ![]() SSH like most security protocols can use different encryption methods, cipher suites, and key generation mechanisms. Under the covers, SSH uses Cipher Suites, Hostkeys, Key Exchange Protocols, Message Authentication Codes (MAC). SSH is what encrypts what you see at the command line interface(CLI). Secure Shell (SSH) is a secure management protocol that Cisco engineers use to connect to and administer IOS XE.
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