HP ProCurve 408, Installation Manual

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Introducing the Switch 408
Switch Operation Overview
matically and stored in the Switch 408’s 1000-entry 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 Switch 408 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 Switch
408 automatically recognizes the change and updates the address
table with the new port locations of the devices. Communication with
the connected devices is thereby automatically maintained.