Which aggregation technology allows the combination of up to two switches into a singular logical switch?

The aggregation technology that allows the combination of up to two switches into a singular logical switch is known as Virtual Switching System (VSS). VSS creates a virtual switch by linking two physical switches, effectively enabling the pair to operate as a single logical device. This configuration enhances network resiliency, simplifies management, and provides increased bandwidth.

When VSS is employed, features such as redundancy and load balancing are achieved without the need for complex spanning tree protocols to manage multiple switch connections. This not only simplifies network design but also results in a more efficient use of network resources. By presenting a single switch to the rest of the network, VSS also simplifies configuration and troubleshooting.

The other options do not serve this specific purpose. While VLANs are utilized to segment a network, Spanning Tree Protocol (STP) is primarily a loop prevention protocol, and Multi-Chassis Link Aggregation (MLAG) allows for multiple switches to be seen as a single entity by the end devices. However, MLAG operates differently than VSS, as it does not inherently create a single control plane across the switches, but rather allows individual switch management while presenting a singular network interface to connected devices.