Bridge port extenders (BPEs) are devices that do not fully process packets, nor make forwarding or filtering decisions. Instead, BPEs simply receive packets from extended ports and forward packets towards the upstream controlling bridge for L2/L3/Policy processing.
Note
Due to the lack of extensive processing performed on BPEs, traffic entering on a BPE extended port that is destined to exit another extended port on the same BPE is forwarded to the controlling bridge (CB), and then forwarded back to the BPE, rather than processed exclusively within the BPE.