# Converting Single Engines to Engine Clusters

You can use a conversion tool to change an existing Single Engine into a Engine Cluster.

The conversion tool:

- Maintains the relationship of the Security Engine element with other configurations in the system, such as VPNs
- Allows you to maintain some existing interface configurations, such as VLANs defined on interfaces
- Minimizes service interruptions.

The following limitations apply when you convert Single Engine elements to Engine Cluster elements:

- It is not possible to combine two Single Engine elements into a Engine Cluster.
- A Single Engine can only be converted to a two-node Engine Cluster. If you want to add more nodes to the cluster, you must add the nodes separately after the conversion.

Due to differences in the supported configurations, the following configurations prevent you from converting from a Single Engine to a Engine Cluster:

Table 1. Unsupported configurations on Engine Clusters
Configuration | Notes
--- | ---
Wireless interfaces | Engine clusters do not support wireless interfaces.
Dynamic IP addresses | Engine clusters can only have static IP addresses. Clusters cannot use a dynamically assigned (DHCP or PPPoE) IP address.
Modem interfaces | Engine clusters do not support integrated mobile broadband modems, such as LTE modems. You must change to a configuration that uses an external mobile broadband modem through an Ethernet connection to convert to a cluster.
Integrated switch | Engine clusters do not support integrated switches. To convert to a cluster, you must change to a configuration that uses an external switch that the engines access through an Ethernet connection.

Note: If you change the control IP address of the existing node after you start the conversion tool, the connection between the engine and the SMC is lost.

The configuration consists of these general steps:

1. Prepare your environment for converting the Single Engine to a Engine Cluster.
2. Prepare interfaces and IP addresses for converting the Single Engine to a Engine Cluster.
3. Convert the Single Engine element to a Engine Cluster element.
4. Activate the new Security Engine configuration on the Engine Cluster.