What is the purpose of GVRP?

[thomson77840]

It seems like you should be able to use GVRP in the following manner:

1.  Create vlans on a "master" switch and use them however you like.

2.  Need more switch space, so you add an additional switch

3.  Enable GVRP on both switches

4.  Connect a cable between the two switches as a trunk that dynamically adds the vlans to the second switch.

5.  USE those vlans on the second switch by joining those dynamic vlans on some of the second switch's ports.

Steps 1-4 all work, but you cannot do step 5, which would seem to me to be the only useful purpose of GVRP.

Anyone here know why GVRP is used?

Thanks.

[mzaccone · Accepted solution]

The way I'm understanding it from playing with it in the lab is that the MAIN purpose of GVRP would be to eliminate the chance for errors in VLAN configuration especially if you're working with large networks.  Once the VLAN is propagated from the "master" switch to the second switch you can then convert the dynamic VLAN to a static VLAN by adding it manually.

[thomson77840]

Thanks for the reply!

I do suppose that could be a good use for it.  It would be nice for it to actually just add those vlans to other switches or be able to quickly use them.  I guess if you're already having to configure which ports are on which vlan, it's not too big of a step to go in and change from dynamic to static on the GVRP VLANs.

[Jo Kern]

my understanding is that when you connect a device which sends tagged frames into the switch and the switch has the vlan not configured, the switch asks the master switch and if the VLAN is there, it configures the vlan on the switch.

maybe i hope for too much.

[thomson77840]

I'll have to test that out.  That actually seems useful.

[lukasz_naumowicz]

HI,

I also have questions about GVRP.

In our lab, SF300 is connected to SRW224G4 via trunk LAG, two VLANs  ID: 2,3 are propagted via trunk link and GVRP.

After GVRP link between switches became operational, VLANs 2 and 3 were propagated to SRW224G4 as dynamic ones. 

From this moment I'm having issues with configuration of SRW224G4.

I've tested two cases:

1. eth port 1 is configured as general port with PVID 2. to this port I've connected computer that doesn't tag packets, so packets when entering switch should get tag: 2 . Unfortunately there is no communication between computer in VLAN2 on the SRW224G4 and computer in VLAN2 on SF300. Computer connected to SRW224G4 can;t get addres from DHCP server in VLAN2(SA520 connected to SF300).

2. eth port 3 configured as trunk port with default PVID 1. To this port I've connected SPA525G phone that is configured to tag packets to VLAN2. Unfortunately in this case we also don;t have communication between phone and SPA9000 (that is connected to VLAN2 on SF300, phone also doesn;t obtain address from DHCP server in VLAN2).

Both devices phone or computer have no problems with communicating in VLAN2 when we connect them to SF300(untagged port for the computer, and voice vlan enabled port for phone). I've also tried to disable vlan 2 as it was voice vlan in my networks but it didn;t bring any results.

Both cases doesn't seem to work, I don't have any other ideas how can we add ports on the access switch(SRW224G4) to VLANs that were dynamically propagated via GVRP from SF300.

Best Regards,

Lukasz

[thomson77840]

From my experience, it seems like although the VLAN is created dynamically on the second switch (in your case the SRW), you cannot use it until you statically add it.

Although it seems like your steps should work, the problem lies with the original reason I opened this thread.  That is, that you cannot use a dynamically created VLAN when assinging port to VLAN or VLAN to port.

In your case I'd suggest as a workaround simply adding the VLAN 2 and 3 statically to the SRW.

I know this defeats our percieved purpose of GVRP, but as of yet, I find GVRP mostly useless.

What were your steps to add VLAN 2 on the trunking port and as PVID for the phone and PC, respectively?  On my switches, I am not even able to add those to ports if they are dynamic VLANs.

[lukasz_naumowicz]

OK, thank you for explanation. If we have to add VLANs statically to every switch that participates in the GVRP this function becomes useless for smaller networks.

> What were your steps to add VLAN 2 on the trunking port and as PVID for the phone and PC, respectively?  On my switches, I am not even able to add > those to ports if they are dynamic VLANs.

You are right, if you try to add ports on the SRW via port to vlan or vlan to port you can't do it for dynamic VLANs.

What you can do is to configure port for the computer as general port, and manually enter the PVID in the interface settings.

When it comes to IP phone which tags frames, I thought that after changing interface settings to trunk, switch will automatically add that trunk to GVRP after receiving frames tagged to vlan 2 from the phone, unfortunately it doesn't work like this.

Best REgards,

Lukasz