Connectivity Guide

● Password-less login is disabled by default. To enable, use the username sshkey or username sshkey filename
commands.
● Configure the list of cipher algorithms using the ip ssh server cipher cipher-list command.
● Configure Key Exchange algorithms using the ip ssh server kex key-exchange-algorithm command.
● Configure hash message authentication code (HMAC) algorithms using the ip ssh server mac hmac-algorithm
command.
● Configure the SSH server listening port using the ip ssh server port port-number command.
● Configure the SSH server to be reachable on the management VRF using the ip ssh server vrf command.
● Configure the SSH login timeout using the ip ssh server login-grace-time seconds command, from 0 to 300;
default 60. To reset the default SSH prompt timer, use the no ip ssh server login-grace-time command.
● Configure the maximum number of authentication attempts using the ip ssh server max-auth-tries number
command, from 0 to 10; default 6. To reset the default, use the no ip ssh server max-auth-tries command.
The max-auth-tries value includes all authentication attempts, including public-key and password. If you enable both,
public-key based authentication and password authentication, the public-key authentication is the default and is tried
first. If it fails, the number of max-auth-tries is reduced by one. In this case, if you configured ip ssh server
max-auth-tries 1, the password prompt does not display.
Regenerate public keys
When enabled, the SSH server generates public keys by default and uses them for client authentication:
● A Rivest, Shamir, and Adelman (RSA) key using 2048 bits.
●
An Elliptic Curve Digital Signature Algorithm (ECDSA) key using 256 bits
● An Ed25519 key using 256 bits
NOTE: RSA1 and DSA keys are not supported on the OS10 SSH server.
An SSH client must exchange the same public key to establish a secure SSH connection to the OS10 switch. If necessary, you
can regenerate the keys used by the SSH server with a customized bit size. You cannot change the default size of the Ed25519
key. The crypto key generate command is available only to the sysadmin and secadmin roles.
1. Regenerate keys for the SSH server in EXEC mode.
crypto ssh-key generate {rsa {2048|3072|4096} | ecdsa {256|384|521} | ed25519}
2. Enter yes at the prompt to overwrite an existing key.
Host key already exists. Overwrite [confirm yes/no]:yes
Generated 2048-bit RSA key
3. Display the SSH public keys in EXEC mode.
show crypto ssh-key
After you regenerate SSH server keys, disable and re-enable the SSH server to use the new keys. Restarting the SSH server
does not impact current OS10 sessions.
Virtual terminal line
Use Virtual terminal line (VTY) to control Telnet or SSH connections to the switch.
Enter VTY mode using the line vty command in CONFIGURATION mode.
OS10(config)# line vty
OS10(config-line-vty)#
Control access to VTY
You can control the Telnet or SSH connections to the switch by applying access lists on VTY lines.
Create IPv4 or IPv6 access lists with permit or deny filters.
Enter VTY mode using the line vty command in CONFIGURATION mode.
Security
759