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Stretched VLAN - Q-in-Q?

sgadsby_1
Occasional Advisor

Stretched VLAN - Q-in-Q?

Hi,

I want my Virtual Machine VLAN to be stretched from site A to site B via our ISP. It seems that Q-in-Q will do this for me, so I have a couple of questions:

1) Can I do routing between a local workstation VLAN & the 'stretched VLAN'?

2) Can we send multiple VLANs up a single trunk, such that VLAN X is forwarded to the other end of our Q-in-Q tunnel (eg. traffic from workstation to Virtual Machine), and untagged traffic is routed as per normal (eg. traffic to Internet)?

Simon.

3 REPLIES
Pieter 't Hart
Honored Contributor

Re: Stretched VLAN - Q-in-Q?

vlan's is layer-2 and routing is layer-3.

The provider will put all packets in the Q-in-Q tunnel.
So all tagged vlan packets going into the provider connection (site-1) come out tagged at the other end (site-2).
Most likely untagged packets come out untagged at the other end (but it may be your provider only accepts tagged packets).
They will not be intercepted by the provider and routed to the internet!
Your provider will suply a second connection for the internet.

If your router between vlans is in site-1, then a packet in vlan-a/site2 is on layer-2 forwarded to site-1.
there it's propagated in vlan-a to the router.
This can route it to the internet or to vlan-b wich may propagate back to site-2.
sgadsby_1
Occasional Advisor

Re: Stretched VLAN - Q-in-Q?

Thanks Pieter -

That makes sense. So basically the ISP has to provide me a dedicated link or VLAN which will be "switched" between site-1 and site-2? In which case, I can stretch a single network without Q-in-Q?
But if I want to send multiple VLANs over the link then I need Q-in Q?
And if I send multiple VLANs with Q-in-Q, does the ISP have to know about it or will a dot1q VLAN that they provide do the job without any special config related to Q-in-Q?

Having read some more of the doco it appears that HP switches capable of Q-in-Q can either be dedicated to Q-in-Q or 'mixed'. If the latter, then the only way for Layer 3 routing in the same chassis to occur between standard VLANs and the Q-in-Q VLAN is to connect nominated ports externally.

Simon.
Pieter 't Hart
Honored Contributor

Re: Stretched VLAN - Q-in-Q?

Hi Simon,

- stretch single network without using Q-in-Q => yes
but this is the providers solution to give you a link within his own vlan-configuration

- inform ISP when adding vlan within Q-in-Q => no, it's like having a normal vlan-trunking port

- mixed within same switch -> have no knowledge/experience with that, but can lookup some articles about that.