Use add hpip virtualPort to add a virtual port between two Passport 4400 units. The purpose of High Performance IP (hpip) is to create a WAN link with minimum overhead in the form of protocol switching and encapsulation. Hpip uses Point-to-Point Protocol (PPP) to create an IP-only connection between two Passport 4400 units. This allows you to collect benchmark performance figures for IP forwarding. You must configure one end of the link as the listener and the other end as the caller to prevent timing issues. This is not a dynamic command so you must reset the Passport 4400 unit in order for the command to take effect.