Cisco Cisco Administrative Workstation Installation Guide

If you used a single IP router instead of two, you introduce a potential single point 
of failure to the contact center site. Loss of the one IP router would stop the flow 
of real-time data from the contact center to the CallRouter and stop the flow of 
monitoring data from the Central Controller to the Admin Workstation. It would 
also prevent the use of Post-Routing and translation routes for this contact center.

One of the two IP routers shown in 

 serves as the default gateway for 

the PG. By default, the PG communicates with that side of the Central Controller. 
The PG must have a static route defined to the other side of the Central Controller 
through the other IP router.

Each PG may contain a modem to allow dial-in access through your ICM support 
provider’s Distributed Diagnostic and Service Network (DDSN). In addition to its 
normal address on the visible network, the PG would then require two additional 
visible LAN addresses for this dial-in access.

Another contact center configuration may be used in cases where IVR systems 
need to be separated due to security concerns or when management of the IVRs 
must be carefully protected. 

 shows an example of such a fault 

tolerant contact center site.