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Types of VLANs
Generic VLAN
Registration
Protocol
4-8
As data passes out of the switch, the switch determines if the
destination port requires the frames to be tagged or untagged. All
traffic coming from and going to the server is tagged. Traffic coming
from and going to the trunk ports is tagged. The traffic that comes
from and goes to the other stations on this network is not tagged.
Mixing Port-based and Tagged VLANs. You can configure the
switch using a combination of port-based and tagged VLANs. A
given port can be a member of multiple VLANs, with the stipulation
that only one of its VLANs uses untagged traffic. In other words, a
port can simultaneously be a member of one port-based VLAN and
multiple tag-based VLANs.
For the purposes of VLAN classification, packets arriving on a port
with an 802.1Q tag containing a VLANid of zero are treated as
untagged.
The Generic VLAN Registration Protocol (GVRP) allows a LAN device
to signal other neighboring devices that it wishes to receive packets
for one or more VLANs. The GVRP protocol is defined as part of the
IEEE 802.1Q Virtual LANs draft standard. The main purpose of the
protocol is to allow switches to automatically discover some of the
VLAN information that would otherwise have to be manually
configured in each switch. GVRP can also be run by network servers.
These servers are usually configured to join several VLANs, and then
signal the network switches of the VLANs of which they want to be
part.
Figure 4-6
illustrates a network using GVRP.
Switch A VLAN Red, Tag 10
1000BASE-X
ACTIVITY
LINK ON
DISABLED
4
5
6
1
2
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8
9
10
11
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A
25
25R
23
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L
25
25R
19
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25R
25
GVRP: "Send
me traffic for
VLAN tag 10."
Figure 4-6 Network Example Using GVRP
Note
10/100BASE-T
ETHERNET SWITCH
WITH GIGABIT
ETHERNET
MDI-X
10/100BASE-TX
POWER
MGMT.
GVRP: "Send
GVRP: "Send
me traffic for
VLAN tag 10."
VLAN tag 10."
Switch B
me traffic for
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