Voice intranet was only contains flat numbering structure in which all extensions have the same length. Now the concept of voice intranet has been extended. With new intranet call routing capability, a voice intranet can be formed by multiple IPX clusters. Each IPX cluster consists of some IPX and has flat numbering structure. Different IPX clusters can have different numbering method. Each cluster can a cluster id that can be used by intranet call routing to route calls from IPX in one cluster to another IPX in another cluster. This is useful for government or large organization to build hierarchical voice intranet. The feature is available in all IPX model after in the release date March 31st, 2009.