Check this KB [URL]
I hope someone has run into this issue in the past and can provide a little guidance here...  I'm trying to add a new CS (CS1) to an existing VNX5700 Unified array that has only CS0. It is running 7.1.80.3 code.  I got the procedure on Solve and went through using the Express DVD on CS1. The first 32 tasks went fine, and then on the last task - "set up ssh keys", it fails with this:   Host key verification failed. Error: 255  Error IM_14505280158 : Non interactive SSH communication failed to          establish from peer to standby Control Station. Description:         SSH communication failed. Action : Do the following to help investigate the issue:          1) Run "/nasmcd/nas_mcd -e emcnasotherCS_i0 check_ssh_connection"             command. If the command succeeds with return status 0, then retry             the upgrade; else go to step 2.          2) If the problem persists or you need assistance, escalate to your             support organization with the failure details. ------------------------------------------------------------------------------------------------------------------------------------ Now CS1 shows reason code 6. Anybody has any idea on how to fix this??? I'm stuck!  Thanks in advance. James
Adding a CS to existing VNX Unified array