Problem ssh user@cisco_switch returns: ssh_rsa_verify: RSA modulus too small: 512 < minimum 768 bits key_verify failed for server_host_key Solution The modulus of the ssh RSA key pair on the switch is too small. If you have access, generate a new key pair on the switch with a larger modulus. Procedure Login with ssh protocol version 1 ( ssh space dash one ): ssh -1 user@cisco_switch (On the switch): enable (On the switch): Authenticate to "Privileged Exec Mode" mode on the switch. (On the switch): conf t (On the switch): crypto key generate rsa general-keys modulus 1024 (On the switch): Press enter to accept that the current key pair for the switch will be replaced. You now should be able to log into the switch with ssh protocol version 2.