IBM Support

IBM AIX: ssh connections to or from AIX fail if EFS is enabled



If EFS is enabled, connecting to or from an AIX® system that uses ssh, sftp, or scp fails.  Connecting from AIX prints "Unsupported protocol sequence".


With ssh verbose logging enabled, the connection fails soon after it prints the message "Sent ALLOW_PKCS12_KEYSTORE_CLIENT_FLAG packet".
With sshd debug logging enabled, the connection fails soon after it logs the message "Packet sent SSH_EFS_KEYSTORE_OPEN".


By default, when EFS is enabled on AIX, the AIX version of OpenSSH sends a request to the remote system for EFS support.  Most SSH implementations end the connection because they do not recognize this type of request.

Resolving The Problem

Add this option to the /etc/ssh/ssh_config file when AIX is the client or /etc/ssh/sshd_config when AIX is the server.
AllowPKCS12KeystoreAutoOpen no
If AIX is the server, sshd must be stopped and restarted with these commands.
stopsrc -s sshd
startsrc -s sshd


If the instructions in this document do not lead to resolution of the problem, follow these instructions to open a case.  The product must be under warranty or have an active and valid support contract.

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Document Location


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Document Information

Modified date:
24 September 2019