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174 Chapter 6: Using ISDN and DDR Technologies
ESF and B8ZS are the default (and most commonly deployed in North America) settings for
the configuration in Example 6-31. For E1 implementations, the most common implementation
is CRC4 and HDB3. If it doesn't work, change the line code and framing appropriately. There
are a finite number of configuration variables. It is much less time consuming to experiment
with the configuration and figure it out than it would be to call the telco and actually get to talk
to someone who knows the appropriate settings for your installation.
Once the controller is configured, you must define the characteristics of the D channel. For
controller t1 0/0, the D channel (as in Example 6-31) is interface serial 0/0:23. The last timeslot
(number 0­23 here) is the D channel in T1 PRI. The D channel in E1 PRI is timeslot 15
(numbered 0­30).
The timeslot numbering scheme has long been the subject of confusion. To aid in dispelling the
confusion, the numbering scheme used at each point is specified. Example 6-32 illustrates the
E1 equivalent configuration.
This interface, in this case serial 0/0:15, carries the protocol specific configuration (that is, the
IP address, the IPX network, and so forth) for protocols that need to traverse this link.
The configuration in Example 6-32 was captured from an AS5300 with eight PRI ports and two
MICA modem blades with 120 modems each. The isdn incoming-voice modem command
specifies that any inbound calls originating from modem users be directed to a MICA modem
installed in this device rather than treated as if an actual ISDN-capable device were issuing a
call setup. This is not to say that a device with bearer capabilities cannot dial into this device
for connectivity. It still can. The AS5300 detects the call type and treats it accordingly.
PRI Incoming Analog Calls on Digital Modems
Up to this point, the discussion has focused on data calls. In other words, the topics have
centered on B channel to B channel calls.
Example 6-32
E1 PRI Configuration
AS5300A(config)#isdn switch-type primary-ni
!
AS5300A(config)#controller e1 0/0
AS5300A(config-controller)#pri-group timeslots 1-30
AS5300A(config-controller)#framing crc4
AS5300A(config-controller)#linecode hdb3
AS5300A(config-controller)#clock source line primary
!
AS5300A(config)#interface serial 0/0:15
AS5300A(config-if)#ip address 10.12.1.1 255.255.255.0
AS5300A(config-if)#isdn incoming-voice modem