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Content 4.2 ISDN
Configuration 4.2.2 Configuring ISDN PRI ISDN PRI is
delivered over a leased T1 or E1 line. The main PRI
configuration tasks are as follows: - Specify the
correct PRI switch type that the router interfaces with at the
CO of the ISDN provider.
- Specify the T1/E1
controller, framing type, and line coding for the facility of
the ISDN provider.
- Set a PRI group timeslot for the
T1/E1 facility and indicate the speed used.
Because
routers connect to PRI using T1/E1, there is no "interface
pri” command. Instead, the physical interface on the router
that connects to the leased line is called a T1 controller, or
an E1 controller, if an E1 line is being used. This controller
must be configured properly in order to communicate with the
carrier network. The ISDN PRI D and PRI B channels are
configured separately from the controller, using the
interface serial command. Use the isdn
switch-type command to specify the ISDN switch used by the
provider to which the PRI connects. As with BRI, this command
can be issued globally or in interface configuration mode. The
table shows the switch types available for ISDN PRI
configuration: Router(config)#isdn switch-type primary-net5
Configuring a T1 or E1 controller is done in four parts:
- From global configuration mode, specify the controller
and the slot/port in the router where the PRI card is located:
Router(config)#controller {t1 | e1}
{slot/port}
Router(config-controller)#
- Configure the framing, line coding, and
clocking, as dictated by the service provider. The
framing command is used to select the frame type used by
the PRI service provider. For T1, use the following command
syntax: Router(config-controller)#framing {sf |
esf} For E1 lines, use the framing command with
the following options: Router(config-controller)#framing
{crc4 | no-crc4} [australia] Use the
linecode command to identify the physical-layer
signaling method on the digital facility of the provider:
Router(config-controller)#linecode {ami |
b8zs| hdb3} In North America, the B8ZS signaling
method is used for T1 carrier facilities. It allows a full 64
kbps for each ISDN channel. In Europe, it is typically HDB3
encoding that is used.
- Configure the specified
interface for PRI operation and the number of fixed timeslots
that are allocated on the digital facility of the provider:
Router(config-controller)#pri-group [timeslots
range] For T1, the range of timeslots used is 1-24. For
E1 the range of timeslots used is 1-31.
- Specify an
interface for PRI D-channel operation. The interface is a
serial interface to a T1/E1 on the router:
Router(config)#interface serial{slot/port: |
unit:}{23 | 15}
Within an E1
or T1 facility, the channels start numbering at 1. The
numbering ranges from 1 to 31 for E1 and 1 to 24 for T1. Serial
interfaces in the Cisco router start numbering at 0. Therefore,
channel 16, the E1 signaling channel, is channel 15 on the
interface. Channel 24, the T1 signaling channel, becomes
channel 23 on the interface. Thus, interface serial 0/0:23
refers to the D channel of a T1 PRI. Subinterfaces, commonly
used with Frame Relay, are designated with a dot, or period.
For example, Serial 0/0.16 is a subinterface. Do not confuse
the channels of a T1 or E1 with subinterfaces. Channels use a
colon instead of a dot to indicate the channel number:
- S0/0.23 refers to a Subinterface
- S0/0:23 refers to
a channel
Lab Activity e-Lab Activity:
isdn switch-type In this activity, the student will
demonstrate how to use the isdn switch-type command.
Web Links Configuring ISDN PRI
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Content 4.2 ISDN
Configuration 4.2.3 Verifying ISDN configuration
Several show commands can be used to verify that the
ISDN configuration has been implemented correctly. To confirm
BRI operations, use the show isdn status command to
inspect the status of the BRI interfaces. This command can be
used after configuring the ISDN BRI to verify that the TE1, or
router, is communicating correctly with the ISDN switch. In the
Figure output, the TEIs have been successfully negotiated and
ISDN Layer 3 is ready to make or receive calls. Verify that
Layer 1 Status is ACTIVE, and that the Layer 2 Status state
MULTIPLE_FRAME_ESTABLISHED appears. This command also displays
the number of active calls. The show isdn active command
displays current call information, including all of the
following: - Called number
- Time until the call
is disconnected
- Advice of charge (AOC)
- Charging units used during the call
- Whether the
AOC information is provided during calls or at end of
calls
The show dialer command displays
information about the dialer interface: - Current call
status
- Dialup timer values
- Dial reason
- Remote device that is connected
The
show interface bri0/0 displays statistics for the BRI
interface configured on the router. Channel specific
information is displayed by putting the channel number at the
end of the command. In this case, the show interface
bri0/0:1 command shows the following: - The B
channel is using PPP encapsulation.
- LCP has negotiated
and is open.
- There are two NCPs running, IPCP and
Cisco Discovery Protocol Control Protocol (CDPCP).
Lab Activity e-Lab Activity: show isdn status In
this activity, the student will demonstrate how to use the
show isdn status command to display the status of all ISDN
interfaces.
Content 4.2 ISDN Configuration
4.2.4 Troubleshooting the ISDN configuration The following
commands are used to debug and troubleshoot the ISDN
configuration: - The debug isdn q921 command
shows data link layer, or Layer 2, messages on the D channel
between the router and the ISDN switch. Use this command if the
show isdn status command does not show Layer 1 as ACTIVE
and Layer 2 as MULTIPLE_FRAME_ESTABLISHED.
- The
debug isdn q931 command shows the exchange of call setup
and teardown messages of the Layer 3 ISDN connection.
The
debug ppp authentication command displays the PPP
authentication protocol messages, including Challenge Handshake
Authentication Protocol (CHAP) packet exchanges and Password
Authentication Protocol (PAP) exchanges. - The debug
ppp negotiation command displays information on PPP traffic
and exchanges while the PPP components are negotiated. This
includes LCP, authentication, and NCP exchanges. A successful
PPP negotiation will first open the LCP state, then
authenticate, and finally negotiate NCP.
- The debug
ppp error command displays protocol errors and error
statistics associated with PPP connection negotiation and
operation. Use the debug ppp commands to troubleshoot a
Layer 2 problem if the show isdn status command does not
indicate an ISDN problem.
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