You receive the "Unable to connect to the management gateway server" error when trying to...

 The mgwd user space process is responsible for managing the cluster configuration and providing the management interface for ONTAP. If this process crashes, it may generate a core dump file in the /mroot/etc/mgwd/core directory of the node. To access this directory, you need to log in to the systemshell, which is a Linux shell that runs on the node. The systemshell can be accessed by logging in to the nodeshell using the node console and then running the systemshell command. The nodeshell is a custom shell that provides access to ONTAP commands and utilities. The service processor and the clustershell are not relevant for collecting core dumps from the mgwd process. References = ONTAP 9 Cluster Administration, page 29-30; ONTAP 9 Troubleshooting Guide, page 23-24.