Establishing a layer 2 trunk link AND layer 3 link between 2 switches - Potential issues?

[ericbkchng]

Hi!

I was recently tasked with designing a new campus network that would integrate with an existing network.

The core switch (Catalyst 6807) for the new campus network is to be connected to the core switch of the existing campus (pls see attached diagram).

Basically, the requirement is that we should establish a layer 3 link between the 2 campuses, but that there is also a need to extend a "security" vlan between the old and new campuses. The distance between the campuses is less than 300m.

My thoughts were to just establish a L3 link between the 2 campuses, and then to establish another L2 trunk between them which only carries the security vlan (and perhaps any other vlan that they might need in the future.) Are there any potential issues if I decide to design the network this way? Or is there a better way to extend the VLAN between the 2 campuses?

Thank you!

[rais]

You can use L2 links with optional SVIs.

The existing core switch should connected to both of the new switches...becoming a distribution switch.

HTH

[ericbkchng]

What if I want the existing security VLAN SVI to continue residing on the existing core switch, and for this security VLAN to be trunked over to the new core switches?

And for the SVIs for the new VLANs on the new core switch to reside on the new core switches, and be routed to the old core switch? 

Any potential issues?

Thanks!

[rais]

I don't see any issues. The way you are currently securing the security VLAN from unauthorized access should continue. STP for security VLAN will continue on to the new switches.

Look into VxLAN as an alternate to extend VLANs across datacenters over existing L3 network.

Rais.

[estowell]

Hi, I realize this topic is 7 years old, and edited 4 years ago, but I'm wondering if this solution worked for you? I'm currently building a 3-tier lab and I'm having issues getting a remote management VLAN to work on my core multi-layer switches. Is a layer 2 trunk between distribution and core switches the solution for getting the management VLAN to be accessible on a layer 3 switch? I understand that for a VLAN to be up/up it must have an active access or trunk port so this is seemingly the only solution I can think of.