GVRP and VLAN trunking

[admincrosbypremier]

I have trunked 3 devices together and enabled GVRP which is showing the active vlans from the main switch. i however cant assign ports learned by GVRP to ports on the other two switches. i have tried this doing vlan to port but the VLAN is not listed which i am confused by as in port to VLAN this can be seen.

could anyone tell me if they have this problem and how to fix it

[admincrosbypremier]

here is what i have done so far.

I have created 7 vlans on a SG-300 which is in layer 3 mode. i have enabled GVRP on all interfaces on that switch. i have set the uplink ports to trunk and then ticked the VLAN registration and dynamic vlan check boxes on both ends of the trunk (from the layer 3 SG to a layer 2 SG).

on the layer two device i have gone to the port that i want to change into vlan 4 and enabled GVRP and checked only the registration checkbox. i have set the port to a access port and I have tried to assign port to vlan but i get Dynamic VLAN cant be modified.

if i untick Dynamic VLAN and add the vlans in manually on the layer two the switch functions as expected. this is really anoying as i dont ever have these issues with VTP and dont want to have to do this onn all 4 switches.

im not sure if im setting this up wrong any help would be apreciated as i have googled but got no hits

[nimusell]

Hi Patrick,

Together with Ivan Bondar (the engineer who is handling your case), we replicated your issue in our lab, and we come to the same conclusions as you do. We will properly document the case with screenshots and error messages and escalate it to the business unit, because unless we all are missing something, this seems to be a bug to me ...

We'll keep you posted through the case, and if a bug report is made, we'll post it here as well for future reference.

Best regards,

Nico Muselle

Sr. Network Engineer - CCNA

[vcappucc]

Greetings,

the way you get access to that VLAN is from a PC or server with a NIC running GVRP.  Dynamic VLANs are exclusively dynamic by nature

Thanks

Victor

[admincrosbypremier]

victor after reading your explination i dont understand why cisco would market that these switches can share vlan information (as you would with VTP) but then be unable to assign any of the ports on that switch that has learnt the vlan via GVRP to a interface. This extract is taken from the Sx300 Admin Manual

"Adjacent VLAN-aware devices can exchange VLAN information with each other
by using Generic VLAN Registration Protocol (GVRP). GVRP is based on the
Generic Attribute Registration Protocol (GARP) and propagates VLAN information
throughout a bridged network.

Since GVRP requires support for tagging, the port must be configured in Trunk
mode or General mode.

When a port joins a VLAN by using GVRP, it is added to the VLAN as a dynamic
member, unless this was expressly forbidden in the VLAN To Port Page. If the
VLAN does not exist, it is dynamically created when Dynamic VLAN creation is
enabled for this port."

This is correct you can pass VLAN information but you cant use it at the other end. why is this implemented on this device when most other devices by cisco use VTP

This does also not address the problem how do you get multiple switches to use the same vlans is this something you have to do statically on each device?

[vcappucc]

Greetings Mr. Lawrence,

GVRP allows the propagation of VLAN information from device to device.  With GVRP, a single switch is manually configured with all the desired  VLANs for the network, and all other switches on the network learn those  VLANs dynamically. An endnode can be plugged into any switch and be  connected to that endnode’s desired VLAN. For endnodes to make use of  GVRP, they need GVRP-aware Network Interface Cards (NICs). The  GVRP-aware NIC is configured with the desired VLAN or VLANs, then  connected to a GVRP-enabled switch. The NIC communicates with the  switch, and VLAN connectivity is established between the NIC and switch.

GVRP, change the ports VLAN ID once a a registered NIC plugs into a switch configured for it, and the way you get access to that VLAN is from a PC or server with a NIC running GVRP.  Dynamic VLANs are exclusively dynamic by nature

GVRP and VTP are two similar but different protocols: VTP's main goal is to propagate VLAN information, but it can also do pruning; GVRP's main goal is to do pruning, but it can also do some limited VLAN propagation and vlan assigment.

For VLAN propagation VTP is more flexible and can be extended to support new features, even proprietary, since it's a Cisco protocol for Enterprise solutions, plus it supports both  802.1q and ISL. Instead, GVRP is more inflexible and is tied to the 802.1q standard for trunking.

Thank you

Victor