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4-1
Chapter 4: Advanced Topics
This ES3616 supports both Layer 2 and Layer 3 switching. These functions, along
with other advanced features are described in this chapter.
Basic Functions of Layer-2 Switching
If the <Destination MAC Address, Source MAC Address> of a received frame is
found in the switch’s distributed flow cache, the incoming frame is switched to the
output port. Otherwise, the switch must pass the frame from the receiving port to
one or more transmitting ports based on the rules for handling VLAN tagged or
untagged frames.
During the switching process, the switch performs multiple steps, including:
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VLAN classification
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Learning
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Filtering
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Forwarding
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Aging
The following sections provide additional information about the tasks that the
switch performs during unicast and multicast switching.
Unicast Switching
The following sections describe VLAN classification, learning, filtering, and
forwarding for unicast switching.
VLAN Classification
When the switch receives a frame, it classifies the frame in one of two ways:
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If the frame is untagged, the switch classifies the frame to an associated VLAN.
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If the frame is tagged, the switch uses the tagged VLAN ID to identify the
broadcasting domain of the frame.
Learning
After VLAN classification, the switch checks the <source MAC address, VLAN>
pair in the switching database (SDB) to see whether this pair is known.
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If it is unknown, the switch inserts the pair into the SDB and learns the <source
MAC address, VLAN>.
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If it is known, the switch checks the pair for a mismatched port ID. If the port ID
associated with the <source MAC address, VLAN> pair in the SDB is different
than the receiving port, the switch modifies the port ID in the SDB and modifies
its management database (MDB) accordingly.
Summary of Contents for ES3616
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