Multi-Chassis Link Aggregation Group (M-LAG) is a high-availability technology on Huawei CloudEngine (CE) series switches, where two switches appear as a single logical device to downstream devices. The peer-link between the M-LAG peers synchronizes critical information to ensure seamless failover if one device fails. Let's evaluate the entries:

A . MAC Address Entries: MAC address tables map device MACs to ports. In M-LAG, synchronizing MAC entries ensures that both switches know the location of connected devices. If one switch fails, the surviving switch can forward Layer 2 traffic without relearning MAC addresses, preventing disruptions. Required.

B . Routing Entries: Routing entries (e.g., OSPF or BGP routes) are maintained at Layer 3 and typically synchronized via routing protocols, not M-LAG peer-link packets. M-LAG operates at Layer 2, and while Layer 3 can be overlaid (e.g., with VXLAN), routing table synchronization is not a standard M-LAG requirement. Not Required.

C . IGMP Entries: IGMP (Internet Group Management Protocol) entries track multicast group memberships. While useful for multicast traffic, they are not critical for basic unicast traffic forwarding in M-LAG failover scenarios. Huawei documentation indicates IGMP synchronization is optional and context-specific, not mandatory for general traffic continuity. Not Required.

D . ARP Entries: ARP (Address Resolution Protocol) entries map IP addresses to MAC addresses, crucial for Layer 2/Layer 3 communication. Synchronizing ARP entries ensures the surviving switch can resolve IP-to-MAC mappings post-failover, avoiding ARP flooding or traffic loss. Required.

Thus, A (MAC address entries) and D (ARP entries) are essential for M-LAG synchronization to maintain traffic forwarding during failover, per Huawei CE switch M-LAG design.