ISDN WAN Connections

These configurations were set up in a lab environment using an Adtran Atlas 550 to simulate WAN connection and the RIPv2 routing protocol. This document will configure both an ISDN BRI connection and an ISDN PRI connection with dial-on-demand routing (DDO), snapshot routing, and B channel aggregation.

Basic Rate Interface

Basic Rate Interface (BRI) Configuration With Dial-on-Demand Routing

This document assumes that basic router configuration has already been completed.

1. Configure the router to use the appropriate ISDN switch types.
   • Router(config)# isdn switch-type switch-type
     • To view information on switch types, see ISDN Switch Types.
2. Configure dialer list to identify interesting traffic.
   • Router(config)# dialer-list dialer-group-number protocol protocol-name permit | deny | list access-list-number
3. Configure BRI interface.
   • Router(config)# interface interface-number
   • Router(config-if)# ip address ip-address subnet-mask
   • Router(config-if)# encapsulation ppp
4. Configure a service profile identifier (SPID).
   • Router(config-if)# isdn spid spid-number local-dial-number
5. Set the Dialer Idle Timeout.
   • Router(config-if)# dialer idle-timeout seconds
     • The dialer idle timeout defaults to 120 seconds. It may need to be changed to a lower value to avoid excessive call charges.
6. Associate the interface to the already created dialer-list
   • Router(config-if)# dialer-group dialer-group-number
7. Configure the Dialer Map
   • Router(config-if)# dialer map protocol next-hop-address name hostname [broadcast] dial-string
     • The dialer map tells the interface what to do with interesting traffic
     • You do not need to enable broadcasts if your routing protocol does not need broadcast.
     • The dial string is the destination telephone number.

Configuring Snapshot Routing

1. Configure a dynamic routing protocol.
   • This document was created using RIPv2.
2. Configure the snapshot server
   • Router(config-if)#snapshot server active-time [dialer]
     • the active-time argument is the amount of time in minutes that routing updates with be exchanged and must be the same between the server and the client.
     • The dialer keyword is an option to allow the client to dial up the server if there is no "interesting" traffic.
3. Configure the snapshot client.
   • Router(config-if)#snapshot client active-time quiet-time [suppress-statechange-updates] [dialer]
     • The quiet-time argument, like the active-time argument, is expressed in minutes and is generally equivalent to the active-time x3.
     • The suppress-statechange-updates option will prevent needless triggered updates in such situations as a line protocol changing states.
   • Router(config-if)#dialer map snapshot sequence number dial-string
     • This command identifies which router to call as the snapshot server.
     • The sequence-number identifies the order in which that server is called in cases where there may be more than one snapshot server. Setting it to 1 would make it the first server to call.
     • The dial-string is the destination snapshot server telephone number.

Configuring B Channel Aggregation

There are two types of B channel aggregation available on Cisco routers. This document was written using Multilink PPP.

• Cisco proprietary BOD uses a proprietary algorithm to calculate a load value and can only be applied outbound.
• Multilink PPP (MLP)uses a standards based algorithm and can be applied inbound, outbound, or either.

1. Configure the load threshold that will trigger the use of the second B channel.
   • Router(config-if)#dialer load-threshold load [inbound | outbound | either]
     • The load argument can be any value between 1 and 255 (A threshold of 50 percent would be expressed as 128).
     • In the case of BOD, the directional keyword is not necessary as BOD can only be applied outbound.
   • Router(config-if)#ppp multilink
     • This step is only necessary when using MLP.

Primary Rate Interface

Configuring Basic PRI

This document assumes that a T1 controller has already been installed in the router.

1. Configure the appropriate switch type
   • The switch type can be configured globally or on the interface. Global configuration will set all ISDN interfaces to that switch type, where as configuring the switch type on an interface will affect only that interface.
2. Router(config)#isdn switch-type switch-type
   • • To view information on switch types, see ISDN Switch Types.
3. Configure the dialer list to identify interesting traffic.
   • Router(config)# dialer-list dialer-group-number protocol protocol-name permit | deny | list access-list-numeber
4. Configure the T1 controller for the service provider's framing and linecode.
   • Router(config)#controller interace
   • Router(config-controller)#framing [sf | esf | crc4 | no-crc4]
   • Router(config-controller)#linecode [ami | b8zf | hdb3]
   • Router(config-controller)#pri-group timeslots range
     • The range argument assigns the range of time slots that are allocated to the RRI. T1 has a range of time slots ranged 1 through 24.
5. Configure the D channel. With 24 channels being numbered from 0 to 23, the D channel is number 23.
   • Router(config)#interface serial 1/0:23
   • Router(config-if)#ip address ip-address subnet-mask
   • Router(config-if)#encapsulation ppp
6. Set the Dialer Idle Timeout.
   • Router(config-if)# dialer idle-timeout seconds
     • The dialer idle timeout defaults to 120 seconds. It may need to be changed to a lower value to avoid excessive call charges.
7. Associate the interface to the already created dialer-list
   • Router(config-if)# dialer-group dialer-group-number
8. Configure the Dialer Map
   • Router(config-if)# dialer map protocol next-hop-address name hostname [broadcast] dial-string
     • The dialer map tells the interface what to do with interesting traffic
     • You do not need to enable broadcasts if your routing protocol does not need broadcast.
     • The dial string is the destination telephone number.
     • A dialer map statement must be configured for each connection that this interface will connect to.

Follow the previous instructions for configuring snapshot routing and B channel aggregation.