How many Arista switches may be a part of a single MLAG domain?

An Arista Multi-Chassis Link Aggregation (MLAG) domain is fundamentally designed as a high-availability pair. It consists of exactly two Arista switches, referred to as MLAG peers. These peers are connected via a dedicated peer-link and synchronize their state information, such as MAC address tables and LACP states, using the MLAG control protocol. This architecture allows the two physical switches to function as a single logical switch from the perspective of a connected device, enabling active-active forwarding, device-level redundancy, and hitless software upgrades. The core design of the MLAG protocol is based on this two-switch pairing.

B. 4: An MLAG domain is strictly limited to two peer switches. Architectures with more than two switches, like a spine-leaf fabric, use different technologies such as EVPN, not a single MLAG domain.

C. 8: This is incorrect. The MLAG protocol is designed for a peer-to-peer relationship between only two switches to ensure state consistency and redundancy.

D. 16: This is incorrect. MLAG is not a stacking technology and does not support more than two switches within a single failure domain.

1. Arista Networks, EOS 4.31.1F Manual (2024), Section: MLAG Introduction, Page 1.

"Multi-chassis link aggregation (MLAG) enables a pair of switches (MLAG peers) to form a high availability system that appears as a single switch on the network."

2. Arista Networks, MLAG - Basic Configuration Guide (2023), Section: Introduction.

"Multi-chassis link aggregation (MLAG) allows a pair of Arista switches to appear as a single, logical switch to a connected device."

3. Arista Networks, MLAG Design and Best Practices (2021), Section: MLAG Overview, Page 4.

"MLAG allows for two switches to be bonded together and act as one. This allows for a connected device to create a port-channel across two separate physical switches."