How do I send ec_console commands to multiple nodes simultaneously?

You can use the "broadcast" and "retrieve" console commands on the cluster manager. This is helpful when needing to gather information from the MTA nodes simultaneously. Run this from the ec_console:

/tmp/2025> broadcast summary  
/tmp/2025> retrieve summary  

This feature works via eccmgr (on port 4809), and the data retrieved from each node is stored in a SQLite database located in /var/log/eccluster/control.cache on the cluster manager.

NOTE: When broadcasting commands, you will not receive any output. For Momentum versions 4.x, the retrieve command will only work if you have enabled Log Aggregation.

Refer here for more information:
https://support.messagesystems.com/docs/web-momo4/cluster.config.operations.eccmgr.console.php