Hi
AFAIK it depends on the kinda of requirement and the kinda scenario in which the ISDN connectivity is being used.
1.if you have only one ISDN line and want to connect 2 different locations create 2 different dialers and make the isdn interface as the member of both the dialers.
2.if you have single isdn line and want to use them up for both dialout and dialin you can again go ahead for the same.
3.if you have multiple isdn lines and if you have multiple locations dialing into ur router then create a single dialer and make the isdn interfaces as the member of the dialer interface.so that from remote they can use different isdn nos and get into your network.(This basically involved rotarty group configs with dialer interfaces)
regds
