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Cisco Unified Contact Center Express Solution Reference Network Design, Release 4.1
Chapter 2      Cisco Unified Contact Center Express Solution Architecture
  Unified CCX Fault Tolerance
The two servers with Recording components must be deployed together on the same VLAN segment.  
Typically these two servers are installed on the same VLAN segment as the CRS and Cisco Unified 
CallManager servers.  In certain scenarios, in an effort to reduce WAN bandwidth, it might make sense 
for the two servers with the Recording components to be deployed at a remote site with a large number 
of agents.  However, if this is done, then both servers must be deployed at this remote site. 
Recording requires a Monitoring component. When SPAN port monitoring is configured for silent 
monitoring, the SPAN port monitoring server forwards the RTP stream to the Recording component. If 
that SPAN port monitoring server fails, recording is not possible. When desktop monitoring is 
configured, the Monitoring component is still required in order to set up the media stream. Any one of 
the six monitoring servers could be used for this purpose. If one or multiple Monitoring components fail, 
recording still works, as long as one server running the Monitoring component is still available in the 
CRS cluster. 
Cold Standby Support
CRS high availability requires that the CRS Engine and Database components and the CTI Managers 
with which the CRS servers communicate should be located in the same Campus LAN and the maximum 
round trip delay between these servers be less than 2 ms.
For disaster recovery deployments where the backup CRS servers need to be in a different geographic 
location, CRS high availability is therefore not supported. However, for this requirement, it is possible 
to deploy identically configured cold standby servers in the disaster recovery site. These cold standby 
servers at the second site should be shut down while the primary servers are in service at the first site. If 
a disaster occurs and the primary site is down, the standby servers are turned on, restored, and become 
the active servers. 
Cold standby is supported for all Unified CCX deployment models described in Chapter 3. For example, 
for the ten-server HA deployment model, ten coldstandby servers can be added on the disaster recovery 
site. 
When deploying cold standby, the following rules apply:
Use theBackup and Recovery System (BARS) tool to backup the primary servers and restore the 
cold standby server. Follow the backup and restore procedure in the Cisco CRS Installation Guide 
when doing this.
The deployment in the disaster recovery site needs to be identical to the deployment in the primary 
site (same number of servers, same server type). 
The standby servers should be shut down if the primary servers are running, and vice versa.
The servers at the disaster recovery site need to have the same IP addresses and hostnames as their 
corresponding servers at the primary site during the restore procedure.
During the restore procedure at the disaster recovery site, the server attempts to write to the LDAP 
directory. If it cannot write to the LDAP directory, the restore fails. 
The deployment at the disaster recovery site needs to follow the Unified CCX rules for design that 
are described in
. For 
example, when deploying with high availability at each site, the CRS Engine and Database 
components and the CTI Managers with which the CRS servers communicate must be located in the 
same Campus LAN and the maximum round trip delay between these servers should be less than 2 
ms.
It might be necessary to modify the Unified CCX configuration. For example, the appropriate region and 
location for the CTI ports might need to be reconfigured for proper CAC and codec negotiation.