14-31
Port-Based Virtual LANs (VLANs) and GVRP
GVRP
Port-Based Virtual LANs
(VLANs) and GVRP
General Operation
When GVRP is enabled on a switch, the VID for any static VLANs configured
on the switch is advertised (using BPDUs—Bridge Protocol Data Units) out
all ports, regardless of whether a port is up or assigned to any particular VLA N.
A GVRP-aware port on another device that receives the adve rtisements over
a link can dynamically join the advertised VLAN.
A dynamic VLAN (that is, a VLAN learned through GVRP) is tagged on the port
on which it was learned. Also, a GVRP-enabled port can forward an advertise-
ment for a VLAN it learned about from other ports on the same switch (internal
source), but the forwarding port will not itself join that VLAN until an
advertisement for that VLAN is received through a link from anot her device
(external source) on that specific port.
Figure 14-20. Example of Forwarding A dvertisements and Dynamic Joining
Note that if a static VLAN is configured on at least one port of a switch, and
that port has established a link with another device, then all ot her ports of that
switch will send advertisements for that VLAN.
Operating Note: When a GVRP-aware port on a switch learns a VID through GVRP from another device, the switch begins
advertising that VID out all of its ports except the port on which the VID was learned.
Core switch with static
VLANs (VID= 1, 2, & 3). Port 2
is a member of V IDs 1, 2, & 3 .
1. Port 2 advertises VIDs 1, 2,
& 3.
2. Port 1 receives advertise-
ment of VIDs 1, 2, & 3 AND
becomes a member of VIDs
1, 2, & 3.
3. Port 3 advertises VIDs 1, 2,
& 3, but port 3 is NOT a
member of VIDs 1, 2, & 3 at
this point.
4. Port 4 receives advertise-
ment of VIDs 1, 2, & 3 AND
becomes a member of VIDs
1, 2, & 3.
5. Port 5 advertises VIDs 1, 2,
& 3, but port 5 is NOT a
member of VIDs 1, 2, & 3 at
this point.
Port 6 is statically configured
to be a member of VID 3.
11. Port 2 receives
advertisement of VID 3. (Port
2 is already statically
configured for VID 3.)
9. Port 3 receives advertise-
ment of VID 3 AND becomes
a member of VID 3. (Still not
a member of VIDs 1 & 2.)
10. Port 1 advertises VID 3.
7. Port 5 receives advertise-
ment of VID 3 AND becomes
a member of VID 3. (Still not
a member of VIDs 1 & 2.)
8. Port 4 advertises VID 3.
6. Port 6 advertises VID 3.
Switch 1
GVRP On
2
Switch 2
GVRP On
3
1
Switch 3
GVRP On
5
4
Static VLAN con-
figured End Device
(NIC or switch)
with GVRP On
6