Previously, both symmetric and asymmetric IRB were implemented as distributed solutions, meaning each IRB functioned as a full-featured device capable of handling both Layer 2 and Layer 3 traffic independently. In this test case, we introduce a centralized Layer 3 gateway. Unlike distributed gateways, the centralized gateway is responsible solely for Layer 3 routing traffic, while leaf PEs manage Layer 2 bridging traffic. Centralized gateways simplify the control plane and are particularly well-suited for small-scale data center networks characterized by limited north-south traffic but a predominance of east-west traffic.

In our test, we simulated two SR-MPLS domains. And two centralized Layer 3 Gateway was deployed. We verified that Layer 3 unicast routing traffic had been transmitted through the two Layer 3 gateways, and that Layer 2 bridging unicast traffic had not been sent out through the Layer 3 Gateways. We also observed no packet loss during the whole procedure.