Understanding how a chassis cluster works is half the battle in attaining acceptable HA levels. The rest concerns configuring a cluster.
To be fair, the configuration is actually quite easy—it’s just a few steps to get the cluster up and running. Setting it up correctly is the key to a stable implementation, and needless to say, rushing through some important steps can cause serious pain later on. So, we suggest that you start with fresh configurations, if possible, even if this means clustering the devices starting with a minimal configuration and then adding on from there.
If there is an existing configuration, set it aside and then create the cluster. After the cluster is running happily, then migrate the configuration back on.
When an administrator enters configuration mode on a standalone SRX, all of the active users who log in to the device can see the configuration and edit it. When each user’s changes can be seen by the other users on the device, it’s called a shared configuration. Once chassis clustering is enabled, the devices must be configured in what is called configure private, or private, mode, which enforces each administrator to see only her own configuration changes. This imposes several restrictions on the end administrator while using configure private mode.
The first notable restriction is that all configuration commits
must be done from the root, or top, of the configuration hierarchy.
Second, the option to do