About The Cluster Subzone; Neighboring The Local Vcs To Another Vcs Cluster - Cisco TelePresence Administrator's Manual

TMS (version 12.6 or later) is mandatory if your cluster is configured to use FindMe or Device Provisioning.
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See VCS Cluster creation and maintenance deployment guide
TMS.

About the Cluster Subzone

When two or more VCSs are clustered together, a new subzone is created within the cluster's Local Zone.
This is the Cluster Subzone (see the diagram in the
the cluster will briefly pass via this subzone during call setup.
The Cluster Subzone is (like the Traversal Subzone) a virtual subzone used for call routing only, and
endpoints cannot register to this subzone. After a call has been established between two peers, the Cluster
Subzone will no longer appear in the call route and the call will appear as having come from (or being routed
to) the Default Subzone.
The two situations in which a call will pass via the Cluster Subzone are:
Calls between two endpoints registered to different peers in the cluster.
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For example, Endpoint A is registered in the Default Subzone to Peer 1. Endpoint B is also registered in the
Default Subzone, but to Peer 2. When A calls B, the call route is shown on Peer 1 as Default Subzone ->
Cluster Subzone, and on Peer 2 as Cluster Subzone -> Default Subzone.
Calls received from outside the cluster by one peer, for an endpoint registered to another peer.
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For example, we have a single VCS for the Branch Office, which is neighbored to a cluster of 4 VCSs at the
Head Office. A user in the Branch Office calls Endpoint A in the Head Office. Endpoint A is registered in the
Default Subzone to Peer 1. The call is received by Peer 2, as it has the lowest resource usage at that
moment. Peer 2 then searches for Endpoint A within the cluster's Local Zone, and finds that it is registered
to Peer 1. Peer 2 then forwards the call to Peer 1, which forwards it to Endpoint A. In this case, on Peer 2
the call route will be shown as Branch Office -> Default Subzone -> Cluster Subzone, and on Peer 1 as
Cluster Subzone -> Default Subzone.
Note that if Call routed mode is set to Optimal and the call is H.323, the call will not appear on Peer 2, and
on Peer 1 the route will be Branch Office > Default Subzone.

Neighboring the local VCS to another VCS cluster

You can neighbor your local VCS (or VCS cluster) to a remote VCS cluster; this remote cluster could be a
neighbor, traversal client, or traversal server to your local VCS. In this case, when a call is received on your
local VCS and is passed via the relevant zone to the remote cluster, it will be routed to whichever peer in that
neighboring cluster has the lowest resource usage. That peer will then forward the call as appropriate to one
of its:
locally registered endpoints (if the endpoint is registered to that peer)
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peers (if the endpoint is registered to another peer in that cluster)
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external zones (if the endpoint has been located elsewhere)
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When configuring a connection to a remote cluster, you create a single zone and configure it with details of all
the peers in the cluster. Adding this information to the zone ensures that the call is passed to that cluster
regardless of the status of the individual peers.
Cisco VCS Administrator Guide (X7.1)
for more information about using clusters with
About clusters section). Any calls between two peers in
Clustering and peers
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