Consider the following simplified scenario that provides Tail End Hop Off (Toll bypass):
A phone is in a site we'll call X and is configured with location of X.
There is a route pattern that uses a route list. In the route list are two route groups each with a single gateway. The first route group contains a gateway in a remote location called Y. The second route group contains a local gateway that is in your local location X.
If a call is attempted to be made by the user that matches the route pattern in the first instance it will try and use the remote gateway in location Y. Now if CAC is used and has determined that there is no available bandwidth between the sites what will happen? I can see two possible answers:
1. The call is blocked
2. The system uses the next route group to try and place the call.
I thought that 2 would be what happens, but cannot find anything definitive that says that. The closest I can find is in the CUCM 5 SRND http://cisco.com/en/US/partner/products/sw/voicesw/ps556/products_implementation_design_guide_chapter09186a00806375f2.html#wp1043613 under the 'Route Lists' heading where is says:
A route list is a prioritized list of route groups that function as alternate paths to a given destination. For example, you can use a route list to provide least-cost routing, where the primary route group in the list offers a lower cost per call and the secondary route group is used only if the primary is unavailable due to an "all trunks busy" condition or insufficient IP WAN resources.
But I'm not sure what 'insufficient IP WAN resources' means whether it refers to CAC or not.