end-to-end vlan and intervlan connectivity

[sarahr202]

Hi everybody.

Please consider the following scenario:

h1------vlan2--AccessSW1-trunk--DistriSW2-----trunk---CoreSw3--------trunk----DistSw4----trunk-----AccessSw5---vlan2----h2

In the above set-up, we have end-to-end vlan2. 

Let say we have vlan3(not shown) connected to Coresw3 directly.  Further assume all distribution and core switches are multilayer switches.The design also requires connectivity between vlan2 and vlan3.

The problem I see is in order to provide communication between vlan2 and vlan3 , we must use layer3 switching at core switch.and configure routing protocol so coresw can learn network mapped to vlan2.  In order to do that, coresw must have layer 3 links not trunks as is the case in our example connected to distribution switches.

Is my analysis correct?

thanks and have a great weekend.

[Reza Sharifi · Accepted solution]

Hi Sarah,

In your scenario above vlan2 span across 5 switches (Too many switches) . While this works, you would usually have vlan2 on -AccessSW1, DistriSW2 and CoreSw3. Then on the other side of the CoreSw3 you create vlan 20 on AccessSw5, DistSw4 and -CoreSw3.  In this case all you have to do is create 2 SVIs (one for vlan 2 and one for vlan 20) and no need for any routing protocols since the SVIs are directly connected interfaces on the -CoreSw3.

If we also use your scenario with vlan2 across all switches and vlan3 directly connected to the CoreSw3.  In this case you also need 2 SVIs on the CoreSw3 and no need for any routing protocols since the SVIs are directly connected interfaces. The router or the multiyear switch would route between vlan2 and 3.

Have a nice weekend!

HTH