Using PPP is one way, but you also may want to try setting the encapsulation on the cisco interface to "encapsulation frame-relay ietf", rather than just "encapsulation frame-relay". The 'IETF' version is the standards-based FR - without the IETF modifier, ciscos use the cisco proprietary FR which Passports, or any other non-cisco device, won't interwork with.
One warning about doing this, though: the encapsulation has to match at both ends of the DLCI. If you have one (cisco) router configured to do the IETF version of FR and the other end expecting the proprietary version, it won't work. So if the cisco that you are connecting to your passport has multiple DLCIs going to remote cisco routers on which have the proprietary version configured, you will need to change EACH remote router interface to also be IETF if you change the central router's interface to be IETF!
This probably won't be the case for you, dragon1293, because it sounds like you have only one connection (FR DLCI, PPP, whatever) that you want to get going. Just a trap to be aware of when you start looking for more than one connection from Cisco to Passport...
