A Novel Passive L1/L2 Edge Loop Detection Observing MAC addresses of L3 Core Switches

A L1 and/or L2 loop in a network may cause congestion and incur communication failures. It is, therefore, important to quickly and accurately detect a loop and locate its origin in order to eliminate the loop. To address this issue, this paper proposes a novel passive loop detection on edge ports of edge switches where end users' routers or terminals are accom-modated. The basic idea of the proposed detection is inspired by the nature that a MAC address of a L3 core switch should never be observed on an edge port. The MAC address is then observed by always-accepting MAC address authentication that can be easily deployed. The proposed detection can, therefore, accurately locate an edge port where a loop is formed, and avoid a failure to notify a network operator of a loop. In addition, the proposed detection can reduce a load on an edge switch more than the existing active detecting methods. Our evaluations in the real campus network have shown that the proposed method can detect the loop even where the existing methods cannot.