VNIP topology is a feature that, for each interface, maps all compatible VNIP peers, their DLCI value, ip address and relative location. The topology is a fundamental prerequisite to applying the VNIP feature set which includes PVC-based delay measurement, diagnostics, and congestion monitoring. With VNIP enabled on an interface the unit will attempt to locate VNIP peers out that port. As peers are discovered and logged the unit will report the topology it has learned on its opposite interface. If VNIP is inactive on one interface it will not engage in any VNIP dialog; however it will continue to listen for topology messages on the inactive interface and will reflect these messages out the opposite interface if VNIP is enabled. With VNIP inactive on both interfaces the unit will transparently pass all VNIP messages. The topology database includes the interface, local DLCI value, remote peer DLCI value, remote peer ip address, and the number of VNIP hops in between. This table also reports the status of other VNIP features as well.