Cabletron Systems SmartSTACK ELS100-24TXM, Инструкция по установке и эксплуатации

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92 Virtual LANs (VLANs) ELS100-24TXM
VLAN Hybrid Ports
A VLAN Hybrid port is used to connect one or more VLAN-aware or
VLAN-unaware devices to the switch. Both tagged and untagged frames
can be received and transmitted on Hybrid ports. Egress ports should
typically be configured as Hybrid ports.
When a frame with an unlearned source MAC address enters a Hybrid
port, the learning of that address and its associated VLAN is dependent
on whether the frame is tagged or not. If the frame is untagged, its source
MAC address is learned as a non-tagging station, with a VLAN ID equal
to the input port PVID. All frames subsequently sent to that MAC address
from this Hybrid port will be untagged. If the frame is tagged, its source
MAC address is learned as a tagging station, with a VLAN ID equal to the
value of the VLAN ID in the tag. All frames subsequently sent to that MAC
address from this Hybrid port will be tagged with that same VLAN ID.
In Example 1 in Figure D-3A, two ports are configured with two different
PVIDs, X and Y. A frame arrives (1) with a tag for VLAN Z. If the
destination MAC address of that frame has already been learned on the
destination port as a tagged station with the same VLAN ID of Z, the frame
is sent out that port (3) with the VLAN Z tag still appended to it. If the
address has not been learned with the VLAN ID of Z on the destination
port, the frame is dropped.
In Example 2 in Figure D-3A, a similar scenario to Example 1 occurs,
except that the incoming frame (1) is tagged with a VLAN Y tag. The frame
is being sent (2) to a port that belongs to VLAN Y. In this case, the
decision to append a VLAN Y tag or not to the outgoing frame depends
on whether the destination MAC address has been learned as a tagged
or as an untagged station. In this example, it was learned as an untagged
station, so the frame is sent out without a tag (3).
Figure D-3. VLAN Hybrid Ports (Examples 1 and 2)
Example 1
X Y
Z
2
1
Z
Z Y
3
Example 2
X Y
Y
2
1
3
H
H H
H
Z
Identifiers
X, Y, Z = VLAN
H = Hybrid
Port