Sự khác biệt chính là rằng PRI không hỗ trợ nhiều thiết bị ISDN trên cùng một dòng, trong khi một mạng BRI hỗ trợ kết nối nhiều thiết bị cùng một dòng. Như thể hiện trong hình , các ngành, nghề PRI thiết bị đầu cuối (TE) kết nối trực tiếp đến các đơn vị dịch vụ dữ liệu dịch vụ Đơn vị , | Enabling Dial-on-Demand Routing DDR Chapter 6 217 bandwidth 64 dialer in-band dialer pool 2 dialer remote-name Router3 dialer string 8358661 class backup dialer load-threshold 127 either dialer-group 1 ppp multilink map-class dialer backup dialer fast-idle 30 dialer hold-queue 20 dialer idle-timeout 180 The first two bold commands in Figure configure the BRI0 interface to be a member of dialer pools 1 and 2. The optional priority parameter can be used to specify that one pool receive priority over another. The priority range is from 0 lowest to 255 highest with a default value of 0. The next two bold commands configure interfaces dialer1 and dialer2 to be members of dialer pools 1 and 2 respectively. Finally the map class backup has been configured. You can see that under the dialer string commands in dialer pools 1 and 2 the class backup parameter has been used. The class parameter associates the map class backup with that interface when that string is dialed. Virtual Profiles The virtual profile feature of DDR is a method of customizing each dial-up connection with its own virtual interface. When using virtual profiles as each user dials in to the network he is assigned his own unique interface. This feature allows for a more scaleable dial-up network. Some of the virtual profiles work if you are using DDR dialer profiles or legacy DDR or even if DDR is not configured. One use of a virtual profile is for a specific user to get a specific IP address and or routing entries. NOTE In the event you are using a dialer profile for a specific user the virtual profile will override the configuration. 218 Chapter 6 Enabling Dial-on-Demand Routing DDR There are two components of a virtual profile the generic component which is information common to all dial-up users including some router configuration and the user-specific component with information about each user obtained from an authentication
