66 Configuring PowerConnect 3524/P and 3548/PPort Default SettingsThe general information for configuring the device ports includes the short description of theauto-negotiation mechanism and the default settings for switching ports.Auto-NegotiationAuto-negotiation enables automatic detection of speed, duplex mode and flow control on all switching10/100/1000BaseT ports. Auto-negotiation is enabled per port by default.Auto-negotiation is a mechanism established between two link partners to enable a port to advertise itstransmission rate, duplex mode and flow control (the flow control default is disabled) abilities to itspartner. The ports then both operate at the highest common denominator between them.If connecting a NIC that does not support auto-negotiation or is not set to auto-negotiation, both thedevice switching port and the NIC must be manually set to the same speed and duplex mode.If the station on the other side of the link attempts to auto-negotiate with a device 100BaseT port that isconfigured to full duplex, the auto-negotiation results in the station attempting to operate in half duplex.MDI/MDIXThe device supports auto-detection of straight through and crossed cables on all switching10/100/1000BaseT ports. The feature is part of the Auto-negotiation and is enabled whenAuto-negotiation is enabled.When the MDI/MDIX (Media Dependent Interface with Crossover) is enabled, the automaticcorrection of errors in cable selection is possible, thus making the distinction between a straightthrough cable and a crossover cable irrelevant. (The standard wiring for end stations is known as MDI(Media Dependent Interface), and the standard wiring for hubs and switches is known as MDIX.Flow ControlThe device supports 802.3x Flow Control for ports configured with the Full Duplex mode. By default,this feature is disabled. It can be enabled per port. The flow control mechanism allows the receiving sideto signal to the transmitting side that transmission must temporarily be halted to prevent bufferoverflow.Back PressureThe device supports back pressure for ports configured with the half duplex mode. By default, thisfeature is disabled. It can be enabled per port. The back-pressure mechanism prevents the sender fromtransmitting additional traffic temporarily. The receiver may occupy a link so it becomes unavailable foradditional traffic.
