An extension to ifOperStatus, for showing faults and partial faliures, including aggregation of upper layer faults (up to but not including L3). The following Pseudo code describes how the MIB value is calculated for different interfaces: if (AdminStatus is down) { XtndOperStatus= adminDown } else if (OperStatus is testing) { XtndOperStatus = testing } else if (This is a backup interface and its currently in dormant state) { XtndOperStatus= dormantDown } else if (OperStatus = down) { XtndOperStatus = faultDown } else switch interface type { case E1/T1: if (XtndOperStatus of any Channel Group over this I/F is (faultDown or partialDownFault)){ XtndOperStatus = partialDownFault } else XtndOperStatus = up break; case USP or Channel Group: if (XtndOperStatus of FR or PPP I/F over this I/F is (faultDown or partialDownFault)){ XtndOperStatus = partialDownFault } else XtndOperStatus = up break; case FastEthernet or loopback: if (XtndKeepAliveStatus is Down) { XtndOperStatus = keepAliveDown } else XtndOperStatus = up break; case PPP or FabricFastEthernet: XtndOperStatus = up break; case Frame Relay: if (XtndOperStatus of any Sub FR over this I/F is (faultDown or partialDownFault)) { XtndOperStatus = partialDownFault } else XtndOperStatus = up break; case Frame Relay Sub I/F: if (at least one DLCI is up, and at least one is down){ XtndOperStatus = partialDownFault } else XtndOperStatus = up break; case Modem: If (modem is undetected) {XtndOperStatus = modemUndetected} elseif (modem is ready to accept calls){XtndOperStatus = modemReady) elseif (a dialer is dialing the modem) {XtndOperStatus = modemDialing} elseif (modem is connected - incoming call) {XtndOperStatus = modemConnectedDialin} elseif (modem is connected - outgoing call) {XtndOperStatus = modemConnectedDialout} }