After adding a new gateway environment to be monitored within ESM we see that the gateway host names show as 'Gateway1' and 'Gateway2' and not their actual host name.
The gateway stores these generic names by default within the ssg mysql database.
Any ESM install
You can modify the default gateway host name stored within the db by executing the following steps:
Connect to that gateway via policy manager->view dashboard->select the 'cluster status' tab
You should see an entry in here referring to the gateway node names as 'Gateway1' , 'Gateway2' etc .. Right click that entry and choose 'Rename Node' , provide the desired host name.
You should see that new host name reflected within the dashboard. If you then relaunch the ESM interface you will now see the gateway host name updated as well.