Excellent post on unofficialaciguide – hightly recommended.
In ACI the external Routing Peer to the router is done through border leaves with a object called L3Out. L3Out has an object in it called the L3Out InstP also known as the External EPG. 1,669 more words
via Understanding Scope Of Prefixes in L3 Out External EPG in ACI —
RedNectar's Blog 