Between which entities is a contract within a Cisco ACI fabric applied?

In Cisco ACI, contracts specify the rules for communication between a consumer EPG and a provider EPG, enabling or restricting traffic flows. Without a contract, communication between EPGs is implicitly denied.

Contracts do not apply directly between an EPG and a bridge domain; bridge domains are used for Layer 2 forwarding within an EPG or between EPGs, while contracts regulate Layer 3 policy enforcement between EPGs.

Contracts are not applied between an EPG and contexts; contexts (VRFs) define the Layer 3 forwarding domain, but contracts govern inter-EPG communication within or across VRFs.

Contracts are not applied between a bridge domain and a context; bridge domains and contexts are networking constructs, whereas contracts are policy constructs applied between logical endpoint groupings.