The following is a sample config for three BRIs in a rotary-group:
interface BRI0 description connected to x1884 no ip address encapsulation ppp dialer rotary-group 2 ! interface BRI1 description connected to pbx line 1888 no ip address encapsulation ppp dialer rotary-group 2 ! interface BRI2 no ip address encapsulation ppp dialer rotary-group 2 ! interface Dialer2 ip address 6.1.1.3 255.255.255.0 encapsulation ppp dialer in-band dialer map ip 6.1.1.1 name dallas 1891 dialer map ip 6.1.1.1 name dallas 1890 dialer map ip 6.1.1.2 name austin 1885 dialer map ip 6.1.1.4 name raleigh 1886 dialer map ip 6.1.1.19 1889 dialer-group 1 ppp authentication chapdialer-list 1 protocol ip permit