Black Box LBG1000A, Manual

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Unicast Switching
VLAN CLASSIFICATION
When the LBG1000A switch receives a frame, it classifies the frame in one of two ways:
- If the frame is untagged, the switch classifies the frame to an associated VLAN.
- 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 the <source MAC address, VLAN> pair is known.
- If it is unknown, the switch inserts the <source MAC address, VLAN> into the SDB and learns the <source MAC address, VLAN>.
- If it is known, the switch checks the <source MAC address, VLAN> 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.
FILTERING
After learning the address, the switch checks:
- Whether the source port or destination port is in the forwarding state.
- Whether the source MAC address or destination MAC address is to be filtered.
- Whether the source port ID is the same as destination port ID.
If any of these conditions are met, the switch drops the receiving. Otherwise, it continues with the forwarding process described
below.
FORWARDING
During the forwarding process, the switch checks whether the <destination MAC address, VLAN> pair is unknown.
- If it is unknown, the switch floods the receiving frame to all ports in the VLAN, excluding the source port.
- If it is known, the switch forwards the receiving frame to the port associated with the <destination MAC address, VLAN> pair. At
the same time, the switch ascertains the individual’s port’s VLAN tagging/untagging configuration and corresponding VLAN ID to
render the appropriate frame tagging when the frame is ready to be transmitted.
Multicast Switching
For multicast switching, the LBG1000A switch checks whether the received frame is a BPDU. If a BPDU is received, the
switch forwards the frame to the CPU for processing by the spanning tree protocol. Otherwise, the switch performs the
following processes:
VLAN CLASSIFICATION
Same as for unicast switching.
LEARNING
Same as for unicast switching.
FILTERING
After learning the address, the LBG1000A switch checks:
- Whether the source port or destination port is not in the forwarding state.
- Whether the source MAC address or destination MAC address is to be filtered.
- Whether the source port ID is the same as destination port ID.
If any of these conditions are met, the LBG1000A switch drops the receiving. Otherwise, it continues with the forwarding process
described below.