I'm configuring a pix firewall 501 and my ISP told me I must configure it with chap with md5 authentication I use vpdn group pppoex ppp authentication chap command but i can't or i don't know how to configure md5. Does Pix firewall 501 is compatible with RFC1994? My firewall has 6.3(2) IOS version. I need to know for talking with my ISP and resolve the conection problem. because if my firewall isn't compatible I try to upgrade or resolve directly with cisco. Thank for any help ASAP.