GVRP |
Using GVRP
When GVRP is enabled on a switch, the VID for any static VLAN 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 VLAN. A GVRP-aware port on another device that receives the advertisements 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 advertisement 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 another device (external source) on that specific port.
If a static VLAN is configured on at least one switch port and that port has established a link with another device, then all other ports of that switch will send advertisements for that VLAN.
![[NOTE: ]](images/note.gif) | NOTE: A port can learn of a dynamic VLAN through devices that are not aware of GVRP. VLANs must be disabled in GVRP-unaware devices to allow tagged packets to pass through. |
Planning for GVRP operation
To set up dynamic VLANs for a segment:
Determine the VLAN topology required for each segment (broadcast domain) on the network.
Determine which VLANs must be static and which can be dynamically propagated.
Determine the devices on which static VLANs must be manually created to propagate VLANs throughout the segment.
Determine security boundaries and how individual ports in the segment are to handle dynamic VLAN advertisements (see Options for handling unknown VLAN advertisements and Controlling VLAN behavior on ports with static VLANs).
Enable GVRP on all devices to be used with dynamic VLANs and configure the appropriate "Unknown VLAN" parameter (Learn, Block, or Disable) for each port.
Configure static VLANs on the switches, where needed, with their per-VLAN parameters (Tagged, Untagged, Auto, and Forbid—see Controlling VLAN behavior on ports with static VLANs) on each port.
Dynamic VLANs will then appear automatically, according to the chosen configuration options.
Convert dynamic VLANs to static VLANs, where dynamic VLANs are to become permanent.
Displaying switch current GVRP configuration (CLI)
Syntax:
show gvrpShows GVRP status (enabled or disabled), current maximum number of VLANs supported and the current Primary VLAN.
Displaying GVRP status with GVRP disabled
switch(config)#: show gvrp GVRP support Maximum VLANs to support [256] : 256 Primary VLAN : DEFAULT_VLAN GVRP Enabled [No] : No
Displaying GVRP status with GVRP enabled
This example shows the output for the show
gvrp command with GVRP enabled. It includes non-default
settings for the Unknown VLAN field for some ports (see Port number
3, 4, 5 below).
switch(config)#: show gvrp GVRP support Maximum VLANs to support [256] : 256 Primary VLAN : DEFAULT_VLAN GVRP Enabled [No] : Yes Port Type | Unknown VLAN Join Leave Leaveall ---- --------- + ------------ ----- ----- -------- 1 10/100TX | Learn 20 300 1000 2 10/100TX | Learn 20 300 1000 3 10/100TX | Block 20 300 1000 4 10/100TX | Disable 20 300 1000 5 10/100TX | Disable 20 300 1000 6 10/100TX | Learn 20 300 1000 7 10/100TX | Learn 20 300 1000
Displaying switch current GVRP configuration (CLI)
Syntax:
show gvrpShows GVRP status (enabled or disabled), current maximum number of VLANs supported and the current Primary VLAN.
Displaying GVRP status with GVRP disabled
switch(config)#: show gvrp GVRP support Maximum VLANs to support [256] : 256 Primary VLAN : DEFAULT_VLAN GVRP Enabled [No] : No
Displaying GVRP status with GVRP enabled
This example shows the output for the show
gvrp command with GVRP enabled. It includes non-default
settings for the Unknown VLAN field for some ports (see Port number
3, 4, 5 below).
switch(config)#: show gvrp GVRP support Maximum VLANs to support [256] : 256 Primary VLAN : DEFAULT_VLAN GVRP Enabled [No] : Yes Port Type | Unknown VLAN Join Leave Leaveall ---- --------- + ------------ ----- ----- -------- 1 10/100TX | Learn 20 300 1000 2 10/100TX | Learn 20 300 1000 3 10/100TX | Block 20 300 1000 4 10/100TX | Disable 20 300 1000 5 10/100TX | Disable 20 300 1000 6 10/100TX | Learn 20 300 1000 7 10/100TX | Learn 20 300 1000
Viewing and configuring GVRP (Menu)
From the Main Menu, select: 2. Switch Configuration ⇒ 8. VLAN Menu ⇒ 1. VLAN Support
Do the following to enable GVRP and display the Unknown VLAN fields:
Press E (for Edit).
Use ↓ to move the cursor to the GVRP Enabled field.
Press the Space bar to select Yes.
Press ↓ again to display the Unknown VLAN fields.
Use the arrow keys to select the port you want and the Space bar to select the Unknown VLAN option for any ports you want to change.
When you finish making configuration changes, press Enter, then S (for Save) to save your changes to the Startup-Config file.
To view or configure static VLANs for GVRP operation, see VLAN operating notes.