Do aggregation layer switches need to be interconnected

Aggregation layer switches are typically interconnected to provide redundancy, load balancing, and high availability in a network.

Purpose of Interconnecting Aggregation Switches

Aggregation switches serve as a bridge between access switches and the core layer, consolidating traffic from multiple access points and forwarding it upstream efficiently . Interconnecting these switches ensures that if one switch fails, traffic can still flow through the other, maintaining network resiliency . This is especially important in large campus networks or data centers where multiple access switches are connected to the aggregation layer.

Methods of Interconnection

1. MCLAG (Multi-Chassis Link Aggregation): Aggregation switches are often deployed in pairs using MCLAG, which allows multiple physical links from access switches to be combined into a single logical link across two aggregation switches. This setup provides both redundancy and load balancing .
2. Link Aggregation (LAG): IEEE 802.3ad LAG or LACP can be used to bundle multiple physical connections between aggregation switches or between aggregation and core switches. This increases bandwidth and ensures failover if one link fails .
3. Stacking: Some aggregation switches support stacking, which allows multiple switches to operate as a single logical unit. This simplifies management and provides device-level backup .

Benefits of Interconnection

• Redundancy: Prevents a single point of failure in the aggregation layer.
• Load Balancing: Distributes traffic across multiple links to optimize bandwidth usage.
• High Availability: Ensures continuous network operation even during maintenance or hardware failure.
• Scalability: Supports growth by allowing additional access switches to connect without redesigning the network .

Conclusion

While it is technically possible to deploy aggregation switches without interconnecting them, best practices recommend interconnecting them using MCLAG, LAG, or stacking to achieve redundancy, load balancing, and high availability. This approach enhances network reliability and performance, particularly in medium to large-scale enterprise or campus networks .