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C-4 Virtual Lans (VLANs)
Writer: Fran Spragens Project: Virtual Lans (VLANs) Comments:
File Name:3324_c.doc Last Saved On:3/16/99 11:47 AM
In example 3 in Figure C-3B, an untagged frame arrives at the left side port (1).
The frame is tagged with a VLAN X tag (2), and comes out Port Y with a
VLAN X tag (3). The ultimate destination of the frame may be on the outgoing
port’s segment or on another segment.
Example 4 in Figure C-3B, is similar to Example 3 except that both ports
(incoming and outgoing) are on VLAN X. The untagged frame arrives at
incoming port X (1), gets tagged with a VLAN X tag (2), and comes outs
VLAN X (3) with the tag stripped off. The packet thus comes in and out of the
switch port untagged, the same as the access port type case in Figure C-2.
Figure C-3B VLAN Hybrid Ports (Examples 3 and 4)
VLAN Application Example
As the network administrator can use VLANs to define user groups regardless
of the physical LAN segment to which they are connected, both hybrid and
access links can further refine traffic flow in a multi-switch environment.
Figure C-4 shows the combination of both hybrid and access links for a
network with three different VLANs. Note that VLAN Y packets are tagged on
the internal (corporate) network, but VLAN Z packets are not. No packets are
tagged on the access links.