ISDN WAN Connections

Basic Rate Interface (BRI)

This was set up in a lab enviroment using an Adtran Atlas 550 to simulate WAN connection. This document will configure an ISDN BRI connection with dial-on-demand routing (DDO), snapshot routing, and B channel aggragation.

BRI Configuration With Dial-on-Demand Routing

1. Basic Router Configuration
2. Configure the router to use the approiate ISDN switch types.
   • Router(config)# isdn switch-type type
     • This configuration uses the basic-ni switch type. To learn about the other switch type, see ISDN Switch Types.
3. Configure dialer list to identifiy intresting traffic.
   • Router(config)# dialer-list dialer-group-number protocol protocol-name permit | deny | list access-list-numeber
4. Configure BRI Interface with encapsulation and authentication settings.
   • Router(config)# interface interface-number
   • Router(config-if)# ip address ip-address subnet-mask
   • Router(config-if)# encapsulation ppp
   • Router(config-if)# ppp authentication chap
5. Congigure a service profile identifier (SPID).
   • Router(config-if)# isdn spid spid-number local-dial-number
6. Set the Dialer Idle Timeout.
   • Router(config-if)# dialer idle-timeout seconds
     • The dialer idle timeout defualts to 120 seconds. It may need to be changed to a lower value to avoid excesive 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.

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 [supress-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.