The class ID (or PCTag) of the source EPG is inserted by the ingress leaf intoany packets going into the fsbric.

Contracts are always enforced m the ingress leaf

The class ID (or PCTag) of the destination EPG is inserted by the ingress leaf into any packets going into the fabric

Contracts are sometimes enforced in the ingress leaf and sometimes in the egress leaf.

Contracts are always enforced m the egress leaf