Refer to the exhibit.

To create an exit point from all tenants using the common tenant and decrease the routing footprint, the following configuration tasks must be completed:

Update the L3Out ExtEPG subnet in the common tenant with flag Shared Route Control Subnet and Aggregate Shared Routes: This configuration allows the subnets to be shared across different VRFs within the common tenant, enabling communication between EPGs that are in different tenants1.

Change contract Ctr-3 scope to Global, consume it by all EPGs, and flag all subnets with flag Shared between VRFs: By changing the scope of contract Ctr-3 to Global, it can be consumed by all EPGs across the fabric. Additionally, flagging all subnets with Shared between VRFs ensures that the subnets can be used by multiple tenants1.

References :=

Cisco Community Discussion on Common Tenant1

Cisco ACI Basic Configuration Guide2

Cisco ACI Configuring Shared L3Outs Documentation