Refer to the exhibit. Cisco ACI fabric is connected to a Cisco Catalyst 3850 Series Switch using EBGP. Server 2 is unable to communicate with Server 1. Leaf-2 fails to learn the external subnet 10.2.2

Configuring 10.2.2.0/24 under the external EPG of the L3Out is used for classifying incoming external traffic and applying contracts, not for ensuring that other internal leaves learn routes.

Implementing a contract between the Server 2 EPG and the L3Out enables communication between them but does not address the underlying issue of Leaf-2 failing to learn external routes in the first place.

Implementing the bridge domain to advertise its subnet ensures that internal subnets are announced to external networks, but it does not solve the problem of Leaf-2 learning external subnets from other L3Outs or internal fabric BGP.

In Cisco ACI, MP-BGP is used internally to distribute routes throughout the fabric. To ensure that external routes learned by one leaf via an L3Out are propagated to all other leaves that need to forward traffic to those external networks, a spine (or spines) must be configured as MP-BGP route reflectors. This allows leaves to learn routes from spines efficiently without requiring a full mesh of BGP peering among all leaves.