Just a little confusion with VLANs :(

[llukman.halimi]

I know that a router is used to send data to different VLANS.

But lets say that we have a group of people in the engineering department and they span over multiple locations and they are in the engineering VLAN. How would they connect to each other I know they are in one broadcast domain and one subnet but I am confused when it says a router is needed to connect different VLANs and not a same VLAN that is spanned across physically?

I'd really appreciated if someone can clear this up for me thanks.

[Joseph W. Doherty]

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You confusion might be because if a VLAN "naturally" (L2) spans multiple locations, no routing is needed between hosts on that VLAN.  If there is routing between locations, VLANs are normally terminated at the routers.  In the latter, you might have the same VLAN number at multiple locations, but with routers, that same VLAN number shouldn't be hosting the same network.

There is a exception to the foregoing.  There are technologies (e.g L2TPv3) to convey a VLAN over a L3 network.  Using such a technology, the VLAN traffic functions as if the VLAN was "naturally" passed between locations.  I.e. the VLAN hosts don't realize that their traffic is being routed between locations.

[llukman.halimi]

Okay what is this supposed to be did I violate some rule or something?

[Joseph W. Doherty]

Huh?

You asked about spanning a L2 domain across sites and while using routers.  If my prior answer didn't answer your question, please ask for clarification. Unsure what "rule or something" you believe you violated.

[JACQUES DU PLESSIS]

If there are any routing between locations, you cannot have the vlans on the same subnet, because the routers will now know where to send the traffic.

Like Joseph said, there are technologies to allow that, we are using otv, but it is not supported by many platforms (I believe ASR and Nexus 7000 are the only ones).