SRX chassis cluster bundles two devices together to provide high-availability. The cluster nodes must be the same model, have the cards placed in the same slots and must run the same software version. In addition at least two interconnect links must be present (one control and one fabric link). In newer releases the SRX supports dual fabric (high-end and branch SRXs) and dual control links (high-end SRXs only). The ports used for fabric link are defined through configuration. The definition of the ports for the control link on the other hand is not so flexible. The high-end SRXs (1000 and 3000 series) have dedicated ports for that and the 5000 series uses the ports on the SPC cards. On the branch SRX devices revenue ports (fixed ones) are converted to control ports.
Hardware preparation (card placement and cabling) is the initial task for creating the cluster. (The following link contains helpful information about cluster interconnections: http://www.juniper.net/techpubs/en_US/junos12.2/topics/task/operational/chassis-cluster-srx-series-hardware-connecting.html) The next step is to enable clustering on the devices. On branch device the configuration must NOT contain any configuration of the interfaces that will be converted to control links for cluster to form correctly. The following commands provide an easy way to get rid of any potential dangerous configuration
- delete interfaces
- delete security
- delete system host-name (leaving the host-name collides with the group configuration)