Cisco Cisco IPCC Web Option Design Guide

You can implement Unified IP IVR port high availability by using any of the following call-forward 
features in Unified CM:

Forward Busy — forwards calls to another port or route point when Unified CM detects that the port 
is busy. This feature can be used to forward calls to another CTI port when a Unified IP IVR CTI 
port is busy due to a Unified IP IVR application problem, such as running out of available CTI ports.

Forward No Answer — forwards calls to another port or route point when Unified CM detects that 
a port has not picked up a call within the timeout period set in Unified CM. This feature can be used 
to forward calls to another CTI port when a Unified IP IVR CTI port is not answering due to a 
Unified IP IVR application problem.

Forward on Failure — forwards calls to another port or route point when Unified CM detects a port 
failure caused by an application error. This feature can be used to forward calls to another CTI port 
when a Unified IP IVR CTI port is busy due to a Unified CM application error.

When using the call forwarding features to implement high availability of Unified IP IVR ports, avoid 
creating a loop in the event that all the Unified IP IVR servers are unavailable. Basically, do not establish 
a path back to the first CTI port that initiated the call forwarding.

You can implement Unified IP IVR high availability through Unified ICM scripts. You can prevent calls 
from queuing to an inactive Unified IP IVR by using the Unified ICM scripts to check the 
Unified IP IVR Peripheral Status before sending the calls to it. For example, you can program a Unified 
ICM script to check if the Unified IP IVR is active by using an IF node or by configuring a Translation 
Route to the Voice Response Unit (VRU) node (by using the consider if field) to select the 
Unified IP IVR with the most idle ports to distribute the calls evenly on a call-by-call basis. This method 
can be modified to load-balance ports across multiple Unified IP IVRs, and it can address all of the 
Unified IP IVRs on the cluster in the same Translation Route or Send to VRU node.

All calls at the Unified IP IVR are dropped if the Unified IP IVR server itself fails. It is important to 
distribute calls across multiple Unified IP IVR servers to minimize the impact of such a failure. In 
Unified IP IVR Release 4.0(x), there is a default script to handle cases where the Unified IP IVR loses 
the link to the IVR Peripheral Gateway, so that the calls are not lost.