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Dual Speed Functionality and Switching
The Ethernet Switch 10/100 Mbps switched RJ45 port auto negotiates
with the connected device for the fastest data transmission rate
supported by both devices. All models of Weidmüller Ethernet Switch
are plug-and-play devices, so that software configuration is not required
at installation, or during maintenance. The half/full duplex mode for the
switched RJ45 ports is user dependent and changes (by auto-
negotiation) to full or half duplex, depending on which transmission
speed is supported by the attached device.
Switching, Filtering, and Forwarding
Each time a packet arrives at one of the switched ports, a decision is
made to either filter or forward the packet. Packets with source and
destination addresses belonging to the same port segment will be
filtered, constraining those packets to one port, and relieving the rest of
the network from the need to process them. A packet with destination
address on another port segment will be forwarded to the appropriate
port, and will not be sent to ports where it is not needed. Packets that
are used in maintaining the operation of the network (such as the
occasional multi-cast packet) are forwarded to all ports. The Ethernet
Switch operates in the store-and-forward switching mode, which
eliminates bad packets and enables peak performance to be achieved
when there is heavy traffic on the network.
Switching and Address Learning
The Ethernet Switch has an address table that can hold up to 1024
addresses, which makes it suitable for use with large networks. The
address tables are self-learning, so that as nodes are added or
removed, or moved from one segment to another, the Ethernet Switch
automatically keeps up with new node locations. An address-aging
algorithm causes the least-used addresses to be deleted in favor of
newer, more frequently used addresses. To reset the address buffer,
power down the unit and then power it back up.
Auto-Negotiation and Speed Sensing
All of the Ethernet Switch RJ45 Ethernet ports independently support
auto-negotiation for speeds in the 10BaseT and 100BaseTX modes,
with operation according to the IEEE 802.3u standard. This means that
some nodes could be operating at 10 Mbps, while at the same time,
other nodes are operating at 100 Mbps. Auto-negotiation takes place
when an RJ45 cable connection is made, and then each time a LINK is
enabled. The Ethernet Switch advertises its capability for using either
10 Mbps or 100 Mbps transmission speeds, with the device at the other
end of the cable expected to advertise in a similar manner. Depending
on what type of device is connected, this will result in agreement to
operate at a speed of either 10 Mbps or 100 Mbps.
Note about possible lost of data packages in case of
“Duplex
mismatching”
If
the Switch’ AutoNeg-Port is connected to a
non-negotiating
device,
then the Switch will set its port transmission speed same as the
connected device but is unable to correctly detect the duplex mode. As
result the port is set to the correct speed but is using always the half
duplex mode as required by the IEEE 802.3u standard in such cases.
For correct transmission the non-negotiating port has to be set to half-
duplex mode (speed either 10 or 100 Mbit/s).
