Hello friend,
An interface pair is a pair of incoming and outgoing interfaces of the same type. After an interface pair is formed, the traffic enters the incoming interface of the interface pair is forwarded out of the outgoing interface in the interface pair, without MAC address table lookup. If the incoming and outgoing interfaces are the same interface, the packets entering the interface are forwarded out of the same interface after being processed. You can refer to the link: https://support.huawei.com/hedex/hdx.do?docid=EDOC1100149308&id=EN-US_TASK_0178931982&lang=en
Hope to help you!