Information Technology Reference
In-Depth Information
All the previous destinations are represented by strings of dialable digits. The dial-plan
must allocate ranges of numbers for all these targets, and CUCM must be configured to
route to them appropriately (including not routing to them, if necessary).
Call-Routing Configuration Elements
The primary components of the CUCM call-routing system are the following:
Key
To p i c
Route Patterns
■
Route Lists
■
Route Groups
■
Gateways/Trunks
■
Route Pattern
A route Pattern matches a string of dialed digits. The pattern may be specific, matching a
single dialable number, or it may be general, matching hundreds of thousands of possible
numbers. This variable precision is configured using wildcard digits in the pattern. Route
Patterns allow the administrator to specify the target of any given string of dialed digits.
Route Patterns are necessary to provide PSTN dial access. They may also be used to inte-
grate the CUCM dial-plan with an existing PBX dial-plan; in this instance, the Route Pat-
tern would match all the DNS (extensions) controlled by the PBX. In fact, a Route Pattern
may be customized to allow users to dial any number and reach any desired end station.
Route Patterns are associated with either a Route List or a Specific Gateway.
Note:
If a Route Pattern is directly associated with a gateway (as opposed to a Route
List), the selected Gateway can no longer be referenced by a Route Group; the gateway is
“locked in” to the Route Pattern. In small deployments, this may not be problematic, but in
large deployments, doing so limits the flexibility of the system.
Route List
A Route List is an ordered list of Route Groups. The first entry in the list is the preferred
call-routing path; if that path is unavailable (due to failure or no circuit/channel available),
if a second choice is configured, it will be used instead. There may be several choices in
the list; each new call uses the choices in top-down order.
The hierarchical order of the Route List entries allows the administrator to provide depth
of coverage for calls while controlling which resources are used for each call. For example,
if the Route Pattern that matches a national long-distance number is associated with a
Route List that lists its first choice as a Route Group providing access to an inexpensive In-
ter-Exchange Carrier (IXC) PRI circuit, the call is routed to that IXC circuit. Subsequent
calls matching the same Route Pattern are also routed to the IXC circuit until no channels
are available.
At that point, the routing request to the IXC is rejected and the Route List's second choice
is tried. If the second choice is a Local Exchange Carrier (LEC) PSTN PRI circuit, the call
