Data Protection Advisor: Data Domain SSH requests fail
Résumé: All Data Protection Advisor (DPA) Data Domain SSH requests for one Data Domain fail with error "Unable to exchange encryption keys."
Symptômes
All DPA Data Domain SSH requests for one Data Domain fail with error "Unable to exchange encryption keys."
The following warning message is seen in dpaagent.log for the Agent that is used to collect from this Data Domain:
WARN 14276.10356 20200103:164719 com.ssh - aapiSSHInitSession(): Error starting ssh session for host <DD_hostname_or_IP>. -5: Unable to exchange encryption keys
Cause
Résolution
In order to successfully communicate using SSH, both devices must use the same cipher or mac set. If a common cipher or mac set cannot be found between the two devices, then the SSH connection fails. The cipher or mac set must be updated on either or both of the devices attempting to communicate to resolve this issue.
Follow the below steps:
- Run the below command on the Data Domain.
adminaccess ssh option show
Its output looks like this:
Option Value
--------------- -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
session-timeout default (infinite)
server-port default (22)
ciphers aes256-cbc,chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com
macs umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com
--------------- -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
- For the ciphers in that output, confirm if they contain any of the below ones.
aes256-cbc, rijndael-cbc@lysator.liu.se, aes192-cbc, aes128-cbc, arcfour128, arcfour,3des-cbc
If not, run the below command on the Data Domain:
adminaccess ssh option set ciphers 'aes256-cbc,<existing_ciphers_on_DD>'
- For the macs in that output, confirm if they contain any of the below ones.
hmac-sha2-256, hmac-sha2-512, hmac-sha1, hmac-sha1-96, hmac-md5, hmac-md5-96
If not, run the below command on the Data Domain.
adminaccess ssh option set macs'hmac-sha2-256,hmac-sha2-512,<existing_macs_on_DD>'