About The Cluster Subzone - Cisco TelePresence Administrator's Manual

Clustering and peers
Size limitations for clusters and provisioning
A VCS cluster of any size supports up to:
10,000 FindMe accounts
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10,000 users for provisioning
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200,000 phonebook entries
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Note that:
VCS appliances (or equivalent VM hardware) can support up to 2,500 device registrations per peer, subject
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to a maximum of 10,000 registrations per cluster. Typically this means one device per FindMe account.
Large VM server deployments can support up to 5,000 device registrations per peer (with a maximum of
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20,000 registrations per cluster). However, you are still limited to 10,000 FindMe accounts/users and
10,000 provisioned devices per cluster.
If you need to provision more than 10,000 devices, your network will require additional VCS clusters with an
appropriately designed and configured dial plan.
See VCS Cluster Creation and Maintenance Deployment Guide
with Cisco 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
peers in 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 signaling optimization is set to On 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.
Cisco VCS Administrator Guide (X8.1.1)
for more information about using clusters
About clusters [p.158] section). Any calls between two
Managing clusters and peers
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