Objective: Learn how to set up Integrated Services Digital Network (ISDN) on Cisco routers.
Lab Equipment: Router 1 and Router 2 from the eRouters menu
1. Connect to Router 1, and assign it a host name of Router1.
Router>enable
Router#conf t
Router(config)#hostname Router1

2. Connect to Router 2, and assign it a host name of Router2.
Router>enable
Router#conf t
Router(config)#hostname Router2

3. Now, set up the connection between Router1 and Router2 using the BRI ports. Assign the BRI 0 interface of Router1 an IP address of 42.34.10.1 with a 255.255.255.0 subnet mask, enable the interface, and then exit interface configuration mode.
Router1(config)#interface BRI0
Router1(config-if)#ip address 42.34.10.1 255.255.255.0
Router1(config-if)#no shut
Router1(config-if)#exit
Router1(config)#

4. Now, connect to Router2, and assign its BRI 0 interface an IP address of 42.34.10.121 with a 255.255.255.0 subnet mask. Enable the interface, and then exit interface configuration mode.
Router2(config)#interface BRI0
Router2(config-if)#ip address 42.34.10.121 255.255.255.0
Router2(config-if)#no shut
Router2(config-if)#exit
Router2(config)#

5. Return to Router1, and start to configure ISDN. First, specify the ISDN switch type that will be used. If you use the Simulator defaults, the switch type is basic-ni. There are two different ways to configure the ISDN switch type that the router should use. You can specify the command globally for all BRI interfaces on the router, or you can make the switch type interface-specific. In this instance, specify the switch type globally on your router.
Router1(config)#isdn switch-type basic-ni

6. configure some specific information for this BRI interface. First, assign it the ISDN Service Profile Identifier (SPID). Set the SPID on the BRI interface of Router1 by using the isdn spid1 command. A SPID is a number supplied by the ISP to identify the line configuration of the BRI service. Each SPID points to line setup and configuration information on the ISP’s ISDN switch. If you use the defaults for the ISDN switch, the SPID for Router1 will be 32177820010100.
Router1(config)#interface bri 0
Router1(config-if)#isdn spid1 32177820010100

7. Now that you have configured the switch type and SPID, Layer 1 connectivity should exist. Layer 1 connectivity occurs between the ISDN switch and the router. To verify that Layer 1 connectivity exists, use the show isdn status command at the privileged mode prompt. Make sure that the Layer 2 state is Multiple_Frame_Established.
Router1(config-if)#exit
Router1(config)#exit
Router1#show isdn status

8. Now, configure the number that will need to be dialed on the ISDN switch to establish a Layer 3 connection; this is called the dialer string. Set the dialer string on Router1’s BRI 0 interface. If you are using the default configuration, use 7782001.
Router1#config t
Router1(config)#interface bri 0
Router1(config-if)#dialer string 7782001

9. Because ISDN costs money when the connection is up, the connection should only be active when it is being used. You can use dialer groups and dialer lists to accomplish this. A dialer list either permits or denies traffic. Specify a dialer list of protocol ip permit; consequently, all IP traffic will be permitted. To set up a dialer list, use the dialer-list command in global configuration mode.
Router1(config-if)#exit
Router1(config)#dialer-list 1 protocol ip permit

10. The dialer list must be associated with an interface. Add the dialer list to the ISDN BRI 0 interface by using the dialer-group 1 command.
Router1(config)#interface bri 0
Router1(config-if)#dialer-group 1

11. Now that you have set up ISDN on Router1, you need to perform the same steps for Router2, but with some slight modifications. Connect to Router2, and specify the ISDN switch type that you will be using. If you use the Simulator defaults, the switch type is basic-ni. Specify the switch type in global configuration mode on the router.
Router2(config)#isdn switch-type basic-ni

12. Next, provide the SPID for this interface. If you use the Simulator defaults for the ISDN switch, the SPID for Router 2 will be 32177820020100.
Router2(config)#interface bri 0
Router2(config-if)#isdn spid1 32177820020100

13. Now that you have set up the switch type and SPID, Layer 1 connectivity should be established. To verify that Layer 1 connectivity exists, use the show isdn status command at the privileged mode prompt. Make sure that the Layer 2 state is Multiple_Frame_Established.
Router2(config-if)#exit
Router2(config)#exit
Router2#show isdn status

14. Now, configure the dialer string that you will need to dial on the ISDN switch in order to establish a Layer 3 connection. Set the dialer string on Router2’s BRI 0 interface. If you are using the default configuration, use 7782002.
Router2#config t
Router2(config)#interface bri 0
Router2(config-if)#dialer string 7782002

15. configure the dialer list named protocol ip permit on Router2 to permit all IP traffic.
Router2(config-if)#exit
Router2(config)#dialer-list 1 protocol ip permit

16. Use the dialer-group 1 command to add the dialer list to the ISDN BRI 0 interface.
Router2(config)#interface bri 0
Router2(config-if)#dialer-group 1

17. Now that both routers are configured for ISDN, see if you can ping the router on the other side of the connection. From Router2, ping Router1’s BRI 0 interface (IP address 42.34.10.1).
Router2(config-if)#exit
Router2(config)#exit
Router2#ping 42.34.10.1

18. If the ping is successful, ISDN is working. Verify this by issuing the show isdn status command on Router2.
Router2#show isdn status
Examine the Layer 3 settings; there should be one active Layer 3 call. You should also see that the SPID is valid in Layer 2. This information is useful for troubleshooting.
 
19. Finally, view the configuration changes you have made by displaying the running configuration.
Router2#show running-config
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