X.25 calls and data transmissions are sent across the Passport WAN. You must configure the physical ports on the Passport 4400 units for X.25 services. Also, you must configure virtual ports for X.25 services to handle the X.25 connections across the WAN. The X.25 traffic is passed transparently through the Passport 6400 unit. One PANL virtual circuit (SPVC) handles all X.25 calls between any two Passport 4400 units.