This Question Provided some valuable insight on how to set the default TTL for IP packets on a system. I would like to do the same thing, but for multicast packets. I do not know if this is possible.
This page indicates that application code can set the multicast TTL with a call to setsockopt() with the flag IP_MULTICAST_TTL, stating further that default value is 1. I want to know if there is a way to set that value at the system level.