Route Pattern (On-Net)
If you are working with multiple sites across a Wide Area Network with connections
like frame or dedicated circuits, you have the ability to implement on-net
Calls. On-net calls are when you make a call that remains within the network
infrastructure.When using on-net, you have the ability to use abbreviated dialing
string in order to complete calls to other offices.This is just for ease of dialing to
the end user. As an example, let’s say you have an office in Seattle that has a
number range of (206) 707-0000 through (206) 707-0999.You would only need
a single route pattern of 70XXX to complete a call to the Seattle office.The
benefit of this is that it only requires one route pattern entry since the Xs work
as wildcards.
The Cisco CallManager will use route patterns to add or remove digits to the
dialed number.The reason for this is that all dialed strings filtered though the
CallManager must have the appropriate number of digits in order to reach
remote sites (even those located on the same WAN).The Cisco CallManager
simply routes the calls based on these addresses.This is also done to make sure
incoming call numbers don’t need to be changed.
If the WAN cannot complete calls (either due to no connectivity or lack of
sufficient bandwidth), the call will be routed over the PSTN (yet another reason
for the route patterns). In some instances, you will need to have an area code
added to the dial-string.When Cisco CallManager was first released, it was only
able to prepend one set of numbers to any dialed string. Because of this, you had
to use the Cisco IOS gateway to insert the area code (and in some instances, the
three-digit exchange). Cisco fixed that with the release of Cisco CallManager
3.0, which can now add or remove numbers based on a per-route-group basis.
So, you can now manage the entire system from one centralized point that can
control the Cisco IOS gateways (and gateways that use the Skinny Gateway
protocol as well).
www.syngress.com