Dear community
In Cisco ACI, when an EPG (Endpoint Group) is extended beyond one VRF (Virtual Routing and Forwarding) instance, its pcTag may be changed from Local scope to Global scope. This is because initially, an EPG is assigned a Local pcTag within its own VRF. However, if the EPG needs to be accessed across multiple VRFs, a Global pcTag is required.
Now, if an existing external EPG1 is connected via L3out and a new external EPG2 is added (like connecting a new WAN), the concern is whether this addition will break communication with the already established external EPG1. Ideally, the external EPG1, which should already be operating on the global pcTag, would not be affected by the new addition. Usually, the communication interruption occurs when the EPG pcTag is migrated from local to global as part of the initial setup, or when a change in network configuration triggers a reevaluation of the pcTag scope. if EPG1 is already using the Global pcTag and the addition of EPG2 does not require changing the pcTag of EPG1, then EPG1 communication should not be interrupted.
Please let me know if you know or have verified this.
