In a Multi-Chassis Link Aggregation (MC-LAG) environment, the Customer Edge (CE) device is connected to two separate Provider Edge (PE) nodes. From the CE's perspective, these multiple physical links appear as a single standard Link Aggregation Group (LAG). The Link Aggregation Control Protocol (LACP), defined in IEEE 802.1AX, is the industry-standard protocol used to negotiate, maintain, and signal the status of the member links within this LAG. The two PE nodes coordinate their LACP system ID and states to present a unified LACP partner to the CE, ensuring seamless operation and failover.

A. MSTP is a Layer 2 loop prevention protocol (IEEE 802.1s) and is not used for signaling the status of links within a LAG.

B. MCLAG is the name of the high-availability architecture itself, not a specific signaling protocol used between the PE and CE.

D. DHCP is a Layer 3 protocol used for dynamic IP address assignment and is unrelated to Layer 2 link aggregation.

E. While the inter-chassis communication between the PE nodes in an MC-LAG group uses a proprietary protocol (ICCP), the communication with the CE uses the standard LACP to ensure interoperability.

1. Nokia 7450 ESS, 7750 SR, 7950 XRS, and VSR Layer 2 Services and EVPN Guide, Release 21.10.R1. Document ID: 3HE 17196 AAAC TQZZA. Section: "MC-LAG and LACP".

Quote/Paraphrase: The guide states, "The CE is connected to the two PE nodes with a regular LAG interface. The CE runs LACP with its peer (the MC-LAG group)... The PE nodes in an MC-LAG group must coordinate the LACP state. This is done over the ICCP channel." This explicitly confirms LACP is used for the PE-CE connection.

2. Nokia Data Center Fabric with SR Linux Cookbook, Release 21.6.1. Document ID: 3HE 17231 AAAB TQZZA. Section: "MC-LAG concepts".

Quote/Paraphrase: In the description of MC-LAG operation, it details that the CE device forms a standard LAG, typically running LACP, with the two upstream switches. The switches synchronize LACP information between them to act as a single logical LACP peer.