Switch Operation Overview; Address Table Operation - HP J4897A Installation Manual

Switch Operation Overview

Address Table Operation

Address Learning. As devices are connected to the switch ports, either
directly or through hubs or other switches that are connected to the switch,
the MAC addresses of those devices are learned automatically and stored in
the Series 2700 Switch's address table. The switch also identifies the number
of the port on which each address is learned so it knows the relative network
location of each device.
Forwarding, Filtering, Flooding. When the switch receives a packet, it
determines the destination address, and looks for the address in the address
table. Based on the port location of that address, the switch then determines
whether to forward, filter-out, or flood the packet.
■ forward - if the destination address is on a different port than the one on
which the packet was received, the packet is forwarded to the destination
port and on to the destination device.
filter out - if the destination address is on the same port as the one on
■
which the packet was received, the packet is filtered out. The switch
thereby isolates local traffic so the rest of the network connected to the
switch does not use bandwidth dealing with unnecessary traffic.
■ flood - whenever a new destination address is found in a packet received
on a port, the destination address will not yet be in the switch's address
table and the Series 2700 Switch cannot know whether to forward or filter
out the packet. In this case, it sends the packet to all the other switch
ports. This is referred to as "flooding". When the destination device
receives the packet, it replies, and the switch learns the new address from
the reply packet. Then, all future packets destined for that address are
forwarded or filtered out appropriately.
Network Moves and Changes. When devices are moved in the network,
and become connected to a different switch port, the Series 2700 Switch
automatically recognizes the change and updates the address table with the
new port location of the device. Communication with the device is automati-
cally maintained, without any address table manipulation being required.
Introducing the HP Procurve Series 2700 Switches
Switch Operation Overview
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