Administrator Guide

Switch Feature Overview 77
Auto-MDI/MDIX Support
The switch supports auto-detection between crossed and straight-through
cables. Media-Dependent Interface (MDI) is the standard wiring for end
stations, and the standard wiring for hubs and switches is known as Media-
Dependent Interface with Crossover (MDIX). Auto-negotiation must be
enabled for MDIX to detect the wiring configuration.
VLAN-Aware MAC-based Switching
Packets arriving from an unknown source address are sent to the CPU and
added to the Hardware Table. Future packets addressed to or from this
address are more efficiently forwarded.
Back Pressure Support
On half-duplex links, a receiver may prevent buffer overflows by jamming the
link so that it is unavailable for additional traffic. On full-duplex links, a
receiver may send a PAUSE frame indicating that the transmitter should
cease transmission of frames for a specified period.
When flow control is enabled, the Dell Networking N-Series switches will
observe received PAUSE frames or jamming signals, but will not issue them
when congested.
Auto-negotiation
Auto-negotiation allows the switch to advertise modes of operation. The
auto-negotiation function provides the means to exchange information
between two switches that share a point-to-point link segment and to
automatically configure both switches to take maximum advantage of their
transmission capabilities.
Dell Networking N-Series switches enhance auto-negotiation by providing
configuration of port advertisement. Port advertisement allows the system
administrator to configure the port speeds that are advertised.
For information about configuring auto-negotiation, see "Port
Characteristics " on page 591.
NOTE: Dell Networking N2000/N3000/N4000 Series switches do not support half-
duplex operation.