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Chapter 23: GARP VLAN Registration Protocol
264 Section VI: Virtual LANs
Figure 35 provides an example of how GVRP works.
Figure 35. GVRP Example
Switches #1 and #3 contain the Sales VLAN, but switch #2 does not.
Consequently, the end nodes of the two parts of the Sales VLANs are
unable to communicate with each other.
Without GVRP, you would need to configure switch #2 by creating the
Sales VLAN on the switch and adding ports 2 and 3 as members of the
VLAN. If you happen to have a large network with a large number of
VLANs, such manual configurations can be cumbersome and time
consuming.
GVRP can make the configurations for you. Here is how GVRP would
resolve the problem in the example.
1. Port 1 on switch #1 sends a PDU to port 2 on switch #2, containing the
VIDs of all the VLANs on the switch. One of the VIDs in the PDU would
be that of the Sales VLAN, VID 11.
2. Switch #2 examines the PDU it receives on port 2 and notes that it
does not have a VLAN with a VID 11. So it creates the VLAN as a
dynamic GVRP VLAN and assigns it a VID 11 and the name
GVRP_VLAN_11. (The name of a dynamic GVRP VLAN has the prefix
“GVRP_VLAN_”, followed by the VID number.) The switch then adds
port 2, the port that received the PDU, as a tagged member of the
VLAN.
3. Switch #2 sends a PDU out port 3 containing all of the VIDs of the
VLANs on the switch, including the new GVRP_VLAN_11 with its VID
of 11. (Note that port 3 is not yet a member of the VLAN. Ports are
added to VLANs when they receive, not send a PDU.)
4. Switch #3 receives the PDU on port 4 and, after examining it, notes
that one of the VLANs on switch #2 has the VID 11, which matches the
VID of an already existing VLAN on the switch. So it does not create
the VLAN because it already exists. It then determines whether the
port that received the PDU, in this case port 4, is a member of the
VLAN. If it is not a member, it automatically adds the port to the VLAN
FAULT
RPS
MASTER
POWER
GBIC
23
GBIC
24
CLASS 1
LASER PRODUCT
STATUS
TERMINAL
PORT
1357911
2 4 6 8 10 12
13 15 17 19 21 23R
14 16 18 20 22 24R
AT-9424T/GB
Gigabit Ethernet Switch
1357911131517192123R
24681012141618202224R
2324
L/A
D/C
D/C
L/A
D/C
L/A
1000 LINK / ACT
HDX /
COL
FDX
10/100 LINK / ACT
PORT ACTIVITY
L/A
1000 LINK / ACT
GBIC
FAULT
RPS
MASTER
POWER
GBIC
23
GBIC
24
CLASS 1
LASER PRODUCT
STATUS
TERMINAL
PORT
1357911
2 4 6 8 10 12
13 15 17 19 21 23R
14 16 18 20 22 24R
AT-9424T/GB
Gigabit Ethernet Switch
1357911131517192123R
24681012141618202224R
2324
L/A
D/C
D/C
L/A
D/C
L/A
1000 LINK / ACT
HDX /
COL
FDX
10/100 LINK / ACT
PORT ACTIVITY
L/A
1000 LINK / ACT
GBIC
FAULT
RPS
MASTER
POWER
GBIC
23
GBIC
24
CLASS 1
LASER PRODUCT
STATUS
TERMINAL
PORT
1357911
24681012
13 15 17 19 21 23R
14 16 18 20 22 24R
AT-9424T/GB
Gigabit Ethernet Switch
1357911131517192123R
24681012141618202224R
2324
L/A
D/C
D/C
L/A
D/C
L/A
1000 LINK / ACT
HDX /
COL
FDX
10/100 LINK / ACT
PORT ACTIVITY
L/A
1000 LINK / ACT
GBIC
Port 1
Port 2
Port 4
Port 3
Switch #3
Static VLAN
Sales VID=11
Switch #1
Static VLAN
Sales VID=11
Switch #2