how to conigure ISDN on cisco router......

It depends on what type of ISDN you want to configure, you only say you want to configure ISDN on router and no details. I will try to help you in general. Below is a sample to configure for ppp callback server on BRI interface. interface BRI0 ip address 7.1.1.7 255.255.255.0 encapsulation ppp dialer callback-secure dialer enable-timeout 2 dialer map ip 7.1.1.8 name yourname class dial1 9383474747 dialer-group 1 ppp callback accept ppp authentication chap Ok below are commands you needed to configure ISDN - dialer outgoing - dialer voice-call - map-class dialer - interface bri - isdn answer1 - isdn caller - isdn calling-number - isdn leased line - isdn not-end-to-end - isdn spid1 - isdn switch-type - pri-group Show commands to see your isdn status - show controllers bri - show interface bri - show isdn