core1/core2 provide L3 transit between DC and Campus fabrics. Each
physical link toward a Border Leaf is subinterfaced (.100 default,
.200 VRF gold). OSPF area 0 in default VRF, eBGP to DC BLs (65005)
and Campus BLs (66005), iBGP between core1 and core2 via Loopback0.
VRF gold uses redistribute connected and VRF-aware eBGP sessions on
.200 subinterfaces to stitch VRF gold end-to-end across fabrics.
