VTP domain issue

Unanswered Question
Jul 9th, 2009

Hello All,

I have a cisco VTP domain setup, incase I decide to add another vendor switch(say nexus/juniper), how can I get them to speak to my core switch as these switches dont support VTP. Manually creating vlan and using dot1q tagging/trunks is what I have in my mind, but since the use of VTP would the new switches be isolated or will they work fine? Please help.

Thanks,

Prakadeesh

I have this problem too.
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Istvan_Rabai Thu, 07/09/2009 - 00:49

Hi Prakadeesh,

VTP is a Cisco proprietary protocol.

You will need to configure the vlans manually in the non-cisco switches.

Also, you will need to use dot1q as the trunking protocol, as ISL is also Cisco proprietary.

Another issue may be the spanning-tree algorithm.

Non-cisco vendors generally do not support the per-vlan spanning-tree+ (PVST+) feature, only the Common Spanning-tree (CST), which means you will have one spanning tree instance for all vlans, but it should work.

Cheers:

Istvan

prakadeesh Thu, 07/09/2009 - 01:15

Thanks Istvan :)

But incase the vendor supports Rapid-pvst+ , then I can still use it as rapid-pvst+ and pvst+ are backward compatible. Am i right?

So VTP domain should nt be a problem, the servers/clients connected to this non-cisco vendor should be able to flow through the cores.

Thanks,

Prakadeesh

Istvan_Rabai Thu, 07/09/2009 - 02:08

Hi Prakadeesh,

In principle, RPVST+ should be backward compatible with PVST+, but I'm not sure in case of non-cisco switches.

VTP frames are sent to a special multicast mac-address. Non-cisco switches should pass those multicast frames without problem. Therefore VTP messages should be propagated between Cisco switches across a non-cisco switch.

Cheers:

Istvan

milan.kulik Thu, 07/09/2009 - 03:04

Hi,

some items you should be careful with:

1) trunk negotiaition

You should configure your Cisco switch to nonegotiate on a trunk to non-Cisco switch.

2) Native VLAN

Cisco proprietary feature on 802.1q trunks. By default, VLAN1 frames are sent untagged.

Other vendors don't support it or must be configured explicitely.

3) STP mode

It might be a problem if the non-Cisco switch is connected to more than on Cisco switches in your topology.

Even if some vendors (Nortel, e.g.) support PVSTP, the implementation can be different (port cost on 3Com, e.g.).

If RPVSTP+ interacting with PVSTP+, it's recommended to use RPVTP+ in the LAN core (i.e., the STP root should be a part of RPVSTP+ cloud) and not vice versa.

HTH,

Milan

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