Using Dialer Interfaces
If you have several physical interfaces on your router that you want to treat as a single dialer, particularly for PPP multilink channel bonding, you can create a logical dialer interface:
Router1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router1(config)#interface BRI0/0
Router1(config-if)#encapsulation ppp
Router1(config-if)#dialer pool-member 1
Router1(config-if)#isdn switch-type basic-ni
Router1(config-if)#isdn spid1 800555123400 5551234
Router1(config-if)#isdn spid2 800555123500 5551235
Router1(config-if)#ppp authentication chap
Router1(config-if)#exit
Router1(config)#interface BRI0/1
Router1(config-if)#encapsulation [...]