Configuring a BRI Trunk Example
In this example, you have been asked to configure a BRI connection to the PSTN according
to the following network requirements. Figure 4-18 presents the topology used in this
example.
222 Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)
V
Router1
ISDN BRI
2 B Channels
+
1 D Channel
Munich
Phone1-1
2001
Phone1-2
2002
PSTN
Figure 4-18 ISDN BRI Configuration Topology Example
The requirements are as follows:
■ Because the ISDN switch is located in Munich, you need to configure the isdn
switch-type as basic-net3 for Germany.
■ The DSP clocking will be synchronized with the WIC in slot 0.
■ Because the possibility exists for the incoming number being sent digit by digit and
not en bloc, you need to configure isdn overlap-receiving.
■ To define incoming calls as voice-only, configure isdn incoming-voice voice. This
will send incoming calls to the DSP resources.
■ If the current configuration is set to the network-side, use the isdn protocol-emulate
user command to switch to user-side ISDN. The user-side setting is the default, so it
is not shown in the configuration.
Perform these steps to build the BRI trunk to the PSTN:
Step 1. Configure DSP clocking so it is synchronized with the PSTN clock.
Step 2. Configure the ISDN switch type according to the country’s ISDN
implementation.
Step 3. Configure ISDN overlap-receiving for countries with variable-length numbering
plans.
Step 4. Configure incoming ISDN calls as voice. The calls will be directly passed to
the DSPs.
Step 5. Configure BRI as user-side, if necessary. This is the default; so it does not
need to be configured under most circumstances.
Step 6. Reset the interface if necessary, depending on the configuration.
Example 4-8 illustrates the completed configuration.
BRI Trunk
Chapter 4: Performing Call Signaling over Digital Voice Ports 223
Router1#clear interface bri0/0
Router1(config)#network-clock-participate wic 0
Router1(config)#interface bri 0/0
Router1(config-if)#isdn switch-type basic-net3
Router1(config-if)#isdn overlap-receiving
Router1(config-if)#isdn incoming-voice voice
Router1(config-if)#isdn protocol-emulate user