Lab 4.9.
4 Configuring ISDN PRI
Objective
In this lab, the student will configure ISDN BRI on the remote site routers and ISDN PRI on the
central site router.
Scenario
The International Travel Agency wants a connection configured between remote offices in Capetown
and London and its corporate network router in SanJose1. The corporate office has just had an ISDN
PRI provisioned so that SanJose1 can handle 23 ISDN BRI and/or V.90 asynchronous dial up calls
simultaneously. The BRIs on the remote routers need to be configured, and the T1 controller and
PRI D channel need to be configured on SanJose1. When the configuration is complete, each router
should be able to dial the other two routers. SanJose1 should be able to receive calls from both
London and Capetown.
Step 1
This lab assumes that SanJose1 has a T1 controller module installed.
Before beginning this lab, it is recommended that the routers be reloaded after erasing their startup
configuration. This will prevent problems that may be caused by residual configurations. Build and
configure the network according to the diagram, but do not configure the PRI and BRI interfaces on
either router yet. Use the Adtran Atlas 550 or similar device to simulate the ISDN cloud. If the Atlas
550 is used, be sure to use straight-through cables. Connect both routers to the BRI module ports of
1-5 CCNP 2: Remote Access v 3.0 - Lab 4.9.4 Copyright 2003, Cisco Systems, Inc.
the Atlas 550, as labeled in the diagram. Connect the T1 controller on SanJose to the T1 PRI port on
the Atlas 550. This connection may require a DB-15-to-RJ45 adapter on the T1 controller module
and the appropriate cable supplied with the Atlas 550.
Step 2
Configure the ISDN PRI connection. Specify the ISDN PRI switch type, which is determined by the
carrier. The ISDN service provider connecting SanJose1 is using a Northern Telecom DMS100. The
switch is running the National ISDN, version 1, software that is identified by the keyword primary-
ni. Enter the following command:
SanJose1(config)#isdn switch-type primary-ni
Next, configure the local username and password database, so that SanJose1 can authenticate the
remote routers with CHAP as follows:
SanJose1(config)#username Capetown password cisco
SanJose1(config)#username London password cisco
Specify what types of traffic will generate a call to the remote router. Configure a dialer list to specify
any IP traffic as interesting with the following command:
SanJose1(config)#dialer-list 1 protocol ip permit
The SanJose1 router must have a route to both the Capetown and London Ethernet networks. Using
the appropriate commands, configure two static routes to the LAN interfaces of these routers.
1. What are the commands to do this?
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Step 3
In this Step, configure the T1 controller. The controller must be configured according to the provider’s
framing and line coding.
In this case, use extended super frame and the binary 8-zero substitution linecode. Also, set the T1
controller to use all timeslots.
Note: Remember that a T1 has twenty-four 64-kbps channels. To configure the PRI controller
issue the following commands:
SanJose1(config)#controller t1 1/0
SanJose1(config-controller)#framing esf
SanJose1(config-controller)#linecode b8zs
SanJose1(config-controller)#pri-group timeslots 1-24
The final part of the configuration is to configure the PRI D channel. This channel is responsible for
call setup and signaling. The D channel uses channel 23, which is the 24th channel, since they are
numbered beginning with 0. Issue the following commands:
SanJose1(config)#interface serial 1/0:23
SanJose1(config-if)#ip address 192.168.16.1 255.255.255.0
SanJose1(config-if)#dialer-group 1
SanJose1(config-if) #dialer load-threshold 1 outbound
SanJose1(config-if)#dialer idle-timeout 60
SanJose1(config-if)#encapsulation ppp
2-5 CCNP 2: Remote Access v 3.0 - Lab 4.9.4 Copyright 2003, Cisco Systems, Inc.
SanJose1(config-if)#ppp multilink
SanJose1(config-if)#ppp authentication chap
Configure dialer map statements as follows, so that the router knows which numbers to dial to reach
specific next-hop IP addresses:
SanJose1(config-if)#dialer map ip 192.168.16.3 name Capetown 5552000
SanJose1(config-if)#dialer map ip 192.168.16.3 name Capetown 5552001
SanJose1(config-if)#dialer map ip 192.168.16.2 name London 5553000
SanJose1(config-if)#dialer map ip 192.168.16.2 name London 5553001
Also configure as follows, static routes on SanJose1 to reach the Spoke office LAN:
SanJose1(config)#ip route 192.168.200.0 255.255.255.0 192.168.16.2
SanJose1(config)#ip route 192.168.216.0 255.255.255.0 192.168.16.3
Finally use the show isdn status command as follows, to verify that communication between the
router and the ISDN switch has been successfully established:
SanJose1#show isdn status
Global ISDN Switchtype = primary-ni
ISDN Serial1/0:23 interface
dsl 0, interface ISDN Switchtype = primary-ni
Layer 1 Status:
ACTIVE
Layer 2 Status:
TEI = 0, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED
Layer 3 Status:
0 Active Layer 3 Call(s)
Activated dsl 0 CCBs = 0
The Free Channel Mask: 0x801FFFFF
Total Allocated ISDN CCBs = 2
1. How is the show isdn status output for layer 2 of a PRI different from a BRI?
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Step 4
Configure both of the remote routers to use the appropriate ISDN switch type, National ISDN-1.
Since PPP encapsulation and CHAP will be used on the B channels, enter username and password
information on both routers. The following configuration is for London:
Note: When configuring Capetown, be sure to substitute the appropriate information.
London(config)#enable password cisco
London(config)#line vty 0 4
London(config-line)#password cisco
London(config-line)#exit
London(config)#isdn switch-type basic-ni
London(config)#interface bri0/0
London(config)#ip address 192.168.16.2 255.255.255.0
London(config-if)#encapsulation ppp
London(config-if)#ppp authentication chap
London(config-if)#isdn spid1 51055530000001 5553000
London(config-if)#isdn spid2 51055530010001 5553001
London(config-if)#dialer-group 1
London(config-if)#dialer idle-timeout 60
London(config-if)#no shutdown
3-5 CCNP 2: Remote Access v 3.0 - Lab 4.9.4 Copyright 2003, Cisco Systems, Inc.
1. PPP is the line encapsulation on the B channels. What is the encapsulation protocol used on the
D channel?
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Configure dialer-list 1 as follows to identify all IP traffic as “interesting” on both routers:
London(config)#dialer-list 1 protocol ip permit
Configure both spoke routers with the username and password of SanJose1, so that they will each
authenticate SanJose1 using CHAP. A static route to the central office LAN must also be configured
on both routers. The following are example commands for Capetown:
Capetown(config)#username SanJose1 password cisco
Capetown(config)#username London password cisco
Capetown(config)#ip route 192.168.0.0 255.255.255.0 192.168.16.1
Capetown(config)#ip route 192.168.200.0 255.255.255.0 192.168.16.2
Finally, configure the BRI interfaces for the remote routers with the appropriate dialer map
commands. The following are the commands required for Capetown:
Capetown(config)#interface bri 0/0
Capetown(config-if)#dialer map ip 192.168.16.1 name SanJose1 5555000
Capetown(config-if)#dialer map ip 192.168.16.2 name London 5553000
Capetown(config-if)#dialer map ip 192.168.16.2 name London 5553001
Step 5
Verify the configuration of the FastEthernet interface on SanJose1. Ping from both Capetown and
London to 192.168.0.1. The pings should be successful. Troubleshoot as necessary.
After the pings, both Capetown and London will be connected to SanJose1 simultaneously. With
multilink configured, Capetown and London should be using both of their B channels.
If either link is disconnected, ping the FastEthernet interface on SanJose1 again. Once both the
Capetown and London links are up, issue the show ip interface brief command as follows
on SanJose1:
SanJose1#show ip interface brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 192.168.0.1 YES NVRAM up up
Serial0/0 unassigned YES NVRAM administratively down down
Serial0/1 unassigned YES NVRAM administratively down down
Serial1/0:0 unassigned YES unset down down
Serial1/0:1 unassigned YES unset down down
Serial1/0:2 unassigned YES unset down down
Serial1/0:3 unassigned YES unset down down
Serial1/0:4 unassigned YES unset down down
Serial1/0:5 unassigned YES unset down down
Serial1/0:6 unassigned YES unset down down
Serial1/0:7 unassigned YES unset down down
Serial1/0:8 unassigned YES unset down down
Serial1/0:9 unassigned YES unset down down
Serial1/0:10 unassigned YES unset down down
Serial1/0:11 unassigned YES unset down down
Serial1/0:12 unassigned YES unset down down
Serial1/0:13 unassigned YES unset down down
Serial1/0:14 unassigned YES unset down down
Serial1/0:15 unassigned YES unset down down
Serial1/0:16 unassigned YES unset down down
Serial1/0:17 unassigned YES unset down down
Serial1/0:18 unassigned YES unset down down
4-5 CCNP 2: Remote Access v 3.0 - Lab 4.9.4 Copyright 2003, Cisco Systems, Inc.
Serial1/0:19 unassigned YES unset up up
Serial1/0:20 unassigned YES unset up up
Serial1/0:21 unassigned YES unset up up
Serial1/0:22 unassigned YES unset up up
Serial1/0:23 192.168.16.1 YES NVRAM up up
Virtual-Access1 unassigned YES TFTP up up
1. According to the output of this command, which channels of the PRI are connected?
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2. Why does Serial1/0:23 have an IP address, and not Serial1/0:22 or Serial1/0:20?
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With both connections active, issue the show dialer command on SanJose1.
3. What is the dialer reason for Serial1/0:19?
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4. What is the dialer reason for Serial1/0:20?
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5. What is the dialer reason for Serial1/0:21?
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6. What is the dialer reason for Serial1/0:22?
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5-5 CCNP 2: Remote Access v 3.0 - Lab 4.9.4 Copyright 2003, Cisco Systems, Inc.
