The Slot 1 is a Extreme Switch X620-16x and Slot 2 is other Switch X620-16x, I configured stacking for two Switch by port 15 and 16
Slot 1-stack#create tunnel tunnel6 gre destination 172.22.0.11 source 172.22.136.3
Error: Stack slot 1 must be removed before GRE tunnels can be configured. Configuration failed on backup Node, command execution aborted!