I urge you to seriously reconsider your design. VPC/MLAG/etc. are attractive because of the ease of making any VLAN available anywhere without the traditional s

I urge you to seriously reconsider your design. VPC/MLAG/etc. are attractive because of the ease of making any VLAN available anywhere without the traditional spanning tree nightmare of doing so. However, you're trading one nightmare for another. Your core or aggregation switches are now stateful, and you've just experienced the results of stateful network components not failing cleanly. I'm not saying an overlay (e.g. VMware NSX née Nicira) is the solution either. I'd suggest rethinking why you need any VLAN anywhere, which is likely the reason for VPC/MLAG. If I'm wrong and you don't put the same VLAN in multiple cabinets, then rip VPC/MLAG out immediately and switch to a pure L3 design. It is so much simpler and consistent with industry best practices.