About Dialing From The Isdn Network To The Ip Network; About Incoming Call Routing - Cisco 3521 Administrator's Manual

Chapter 4 Using the Cisco IPVC 3500 Series Gateway
Figure 4-1
This number string consists of:
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About Dialing from the ISDN Network to the IP Network

The Cisco IPVC 3500 Series Gateway is responsible for routing incoming calls to the requested H.323
endpoints on the IP network.
ISDN terminals or phones access the gateway using phone numbers. The gateway Integrated Services
Digital Network (ISDN) port connects directly to an ISDN line that the ISDN provider or telephone
company assigns at least one phone number. BRI ISDN lines have two B channels that can be identified
by the same number of by two different numbers. PRI ISDN lines have 23 (T1) or 30 (E1) channels that
may be identified by the same number or by a range of numbers.
When a terminal or phone on the ISDN network wants to reach an IP endpoint, it has to dial at least one
of the phone numbers assigned to the ISDN line connected to the gateway PRI or BRI ISDN port.

About Incoming Call Routing

When a call originating on the ISDN network reaches the Cisco IPVC 3500 Series Gateway, the gateway
routes it to an IP network endpoint. This is achieved through one of several incoming call routing
methods that the gateway supports. You can enable any number of routing methods for each port, but at
least one method must be enabled for incoming calls to be routed through that port. The gateway routes
an incoming call from the ISDN network according to the routing methods enabled for the ISDN port,
following this order of priority: DID − − >TCS4 − − >IVR− − >Default Extension.
If a routing method fails, the gateway automatically tries to route the call through the next routing
method in line. If all methods fail, the call is rejected. The call might also be rejected if the gateway
routes the call to an endpoint that is busy or not available.
Table 4-1
Administrator's Guide for Cisco IPVC 3521 BRI Gateway, Cisco IPVC 3526 PRI Gateway, and Cisco IPVC 3540 PRI Gateway
OL-7995-01
TCS4 Dialing
Endpoint
1
IP
9—The voice call service prefix in Gateway A in Zone A.
82—The service prefix for a 2B video call in Gateway A in Zone A.
5645000—The number of the destination Gateway B on the public ISDN network.
^—The TCS4 delimiter configured in Gateway A.
3333—The E.164 number of the destination IP Endpoint 2.
explains the routing methods.
About Dialing from the ISDN Network to the IP Network
Gateway
Gateway
A 5645000
Public
ISDN
Endpoint
B 2
3333
IP
4-3