Message Routing with authentication enabled will fail between an appliance running LMI 4.9 and an appliance running LMI 5.1. The upstream appliance will show the Tunnel Status as "Fail to connect" and the downstream appliance will show the Tunnel Status as "Peer error: failed to perform client challenge." This error is because version 4.9 uses Blowfish encryption whereas version 5.1 uses AES. 

Note: Even if "Enable Encryption" is set to No, Authentication still uses encryption to complete the connection.

To forward messages between a 4.9 appliance and a 5.1 appliance, you must reconfigure the 5.1 appliance to use Blowfish encryption:

1. Login to the appliance CLI as "toor."
2. Backup the lltunnel.conf as shown in this command:

$ cp /loglogic/conf/ll_tunnel.conf /loglogic/conf/ll_tunnel.conf.ORIG

3. Edit /loglogic/conf/ll_tunnel.conf to include this line:

encrypt 0

4. Save the file and restart the application to pick up the change:

$ mtask stop; mtask start