# Upgrade Cluster Element Software

The following software requirements apply to a cluster:

- To increase the number of elements in a cluster beyond 250, you must first upgrade all elements in the cluster to 3300 ICP Release 8.0 UR3 or later. Then, you must enable 999 as the "Maximum Elements per Cluster" in the License and Option Selection form of each element. Thus, to add the 251st node to a 999 node cluster, the previous 250 nodes must first be upgraded to Release 8.0 UR3 or later software and be configured as nodes to support a 999 node cluster. This will ensure the successful distribution of Remote Directory Numbers (RDN) throughout the cluster when the 28502nd RDN is added.

- To support the management of embedded device resiliency from the 3300 System Administration Tool, you must upgrade all elements in the cluster to MCD Release 4.0 or later software. In addition, all elements in the cluster must support Remote Directory Number (RDN) Synchronization.

- Following a software upgrade (or downgrade), clear your browser cache to remove any stale data that could otherwise prevent you from initiating an SDS synchronization. A grayed-out Sync button is an indication that the cache needs clearing.

Proceed to Synchronize Data with SDS.