This read-write INTEGER enables or disables the SmartStack trunking protocol, an extension to standard Spanning Tree, on the port. An administrator sets it to combine multiple physical links into a single logical trunk for redundancy and added bandwidth between two ELS-100 units. For example, enabling kxprotoTrunking on two ports connecting a pair of stacked switches lets those links form a resilient trunk group instead of operating as independent, potentially loop-prone paths.