config vlan

It's been too  long since I took Cisco, and I am sure this can be done but cannot recall how to do it, with subnets on different sides of the router/s.  I will not be doing it myself, but am advising as others say it cannot be done.   I do not need details, but only confirmation that this can happen.

This is a Cisco shop.  Bld A and Bld B are not connected directly.  I am not sure of all of topology, but basically they are in the same network but different subnets, and are connected to a router in Area C.  We need to connect a few ports on BldA/Switch1,  to ports on BldB/Switch2 so that they are a VLan.
JerryC101Asked:
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Robert Sutton JrConnect With a Mentor Senior Network ManagerCommented:
Trunking using ISL?

What types(Model #) of devices are you referring too?

FWIW:
A trunk is a point-to-point link between the switch and another networking device. Trunks carry the traffic of multiple VLANs over a single link and allow you to extend VLANs across an entire network. Two trunking encapsulations are available on all Ethernet ports:

Inter-Switch Link (ISL)—ISL is a Cisco-proprietary trunking encapsulation.
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Ken BooneNetwork ConsultantCommented:
If you are going through a router then NO as vlans do not span a layer 3 interface.
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Ken BooneNetwork ConsultantCommented:
Yea I thought about bridging it over, but that sounds overly complicated for where he is at...
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JerryC101Author Commented:
If you are going through a router then NO as vlans do not span a layer 3 interface.

Although not untrue, it was my understanding that in an enterprise, routers can be configured to allow VLans across routers.
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Robert Sutton JrSenior Network ManagerCommented:
See my comment above that since what you are describing is DIRECTLY connecting the two switch ports.
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Ken BooneConnect With a Mentor Network ConsultantCommented:
A vlan in itself will not span a layer 3 interface.  A router as mentioned can act as a bridge however in which it could bridge between the two switches, thereby connecting 2 disjointed vlans together to be on the same layer 3 subnet.

Since he apparently needs the router to route traffic between buildings he would then need to route & bridge..  Now things get more complicated.
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JerryC101Author Commented:
See my comment above that since what you are describing is DIRECTLY connecting the two switch ports.

...and are connected to a router in Area C. We need to connect a few ports on BldA/Switch1,  to ports on BldB/Switch2 so that they are a VLan.

So thanks but no, I did not describe directly connecting the two switch ports.
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