Dell PowerConnect 5448 User's Guide - Page 38

MDI/MDIX, Flow Control, Back Pressure, Switching Port Default Settings

Page 38 highlights

If the station on the other side of the link attempts to auto-negotiate with a device 10/100/1000BaseT port that is configured to full duplex, the auto-negotiation results in the station attempting to operate in half duplex. MDI/MDIX The device supports auto-detection of straight through and crossed cables on all switching 10/100/1000BaseT ports. The feature is part of the Auto-negotiation and is enabled when Auto-negotiation is enabled. When the MDI/MDIX (Media Dependent Interface with Crossover) is enabled, the automatic correction of errors in cable selection is possible, making the distinction between a straight through 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 Control The 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 side to signal to the transmitting side that transmission must temporarily be halted to prevent buffer overflow. Back Pressure The device supports back pressure for ports configured to half duplex mode. By default, this feature is disabled. It can be enabled per port. The back pressure mechanism prevents the transmitting side from transmitting additional traffic temporarily. The receiving side may occupy a link so it becomes unavailable for additional traffic. Switching Port Default Settings The following table gives the port default settings. Table 3-3. Port Default Settings Function Port speed and mode Port forwarding state Port tagging Flow Control Back Pressure Default Setting 10/100/1000BaseT copper: auto-negotiation full duplex Enabled No tagging Off (disabled on ingress) Off (disabled on ingress) 38 Installing the PowerConnect Device

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38
Installing the PowerConnect Device
If the station on the other side of the link attempts to auto-negotiate with a device 10/100/1000BaseT
port that is configured to full duplex, the auto-negotiation results in the station attempting to operate in
half duplex.
MDI/MDIX
The device supports auto-detection of straight through and crossed cables on all switching
10/100/1000BaseT ports. The feature is part of the Auto-negotiation and is enabled when Auto-negotiation
is enabled.
When the MDI/MDIX (Media Dependent Interface with Crossover) is enabled, the automatic
correction of errors in cable selection is possible, making the distinction between a straight through
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 Control
The 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 side
to signal to the transmitting side that transmission must temporarily be halted to prevent buffer
overflow.
Back Pressure
The device supports back pressure for ports configured to half duplex mode. By default, this feature is
disabled. It can be enabled per port. The back pressure mechanism prevents the transmitting side from
transmitting additional traffic temporarily. The receiving side may occupy a link so it becomes
unavailable for additional traffic.
Switching Port Default Settings
The following table gives the port default settings.
Table 3-3.
Port Default Settings
Function
Default Setting
Port speed and mode
10/100/1000BaseT copper: auto-negotiation full duplex
Port forwarding state
Enabled
Port tagging
No tagging
Flow Control
Off (disabled on ingress)
Back Pressure
Off (disabled on ingress)