Sending VLAN traffic between two different ISPs

[christopher.minner]

Hello, currently my team is  using one ISP for two sister companies right next to each other. Company A houses the core switch, ASA, ISP router, CCME, WLC, etc. Company B has a switch using a Tengigabitethernet port as a trunk to pass traffic back to the core switch at Company A. All of the VLAN interface configurations between both companies are stored on the core switch at Company A. Both companies use different VLANs(2&4) for access ports but they share the same Voice VLAN(8). Attached is a quick diagram to complement my writing with some more IP info.

My main question is, if I set up a new ISP at Company B(with a new ASA of course) and keep the same trunk in place, will I need to create a new VLAN scheme for Company B? I wasn't sure if there would be any issues because these two companies share all of the same VLANs such as voice, printers, temperature control sensors. The only VLAN that's really different is the access ports.

Thank you and best regards,

Chris

[Richard Burts]

Chris

There are many things about the environment and about your requirements that we do not know and this makes it difficult to give really good answers to your question. Does the switch at company B have the ability to make layer 3 routing decisions or is it just a layer 2 switch? How do you want company B to work? Do you want just their Internet traffic to use the new ISP and all other traffic to continue to flow through company A?

Pretty clearly there will be need for a new vlan at company B to use for the new ASA and second ISP connection. But I am not sure that there would need to be any changes in the existing vlans used for company B. If the switch for company B is capable of layer 3 routing then it should be fairly straightforward to implement logic that would route Internet traffic from company B to the new ISP. If the switch is just layer 2 only then it gets more complicated in determining how the routing should work.

HTH

Rick

[christopher.minner]

Hey Rick, thank you for the info. Yes the switches at Company B are L3 and I want to use them to route internet traffic through the ISP and all other traffic back to the core at Company A. I figured this should be pretty simple but I wasn't sure if those VLANs would cause issues. 

Best regards,

Chris

[Richard Burts]

Chris

The drawing that you posted shows an access vlan for company B but does not show the access vlan for company A. So it is hard to be sure how things are working. As long as the vlan (and IP subnet) for access for company A is different from the vlan (and IP subnet) at company B it should be possible to set up routing logic on the layer 3 switch for company B to send their Internet traffic through the new ISP without requiring any changes in existing vlans.

HTH

Rick