In Huawei M-LAG design, the peer-link is a critical connection between two M-LAG member devices used for synchronization of control information (such as MAC address tables, ARP entries, and state information) and for forwarding certain types of traffic like broadcast, multicast, and unknown unicast (BUM) traffic when necessary.

However, to prevent traffic loops and duplication , Huawei enforces strict isolation between peer-link interfaces and dual-homed M-LAG member interfaces . Specifically, this relationship is bidirectionally isolated , meaning traffic received from a dual-homed interface is not forwarded to the peer-link and then back to another dual-homed interface, and vice versa.

This bidirectional isolation ensures:

Loop prevention without relying on STP

Avoidance of duplicate packet forwarding

Efficient traffic handling in active-active scenarios

BUM traffic is only forwarded over the peer-link under controlled conditions, not blindly between all interfaces. Huawei CloudFabric best practices emphasize this isolation to maintain stable and predictable forwarding behavior in M-LAG deployments.

Therefore, the correct answer is C (Bidirectionally isolated) .