This is in response to the below thread.
https://www-secure.symantec.com/connect/forums/gup-migration-11-121
There seems to be some confusion from customers about backwards and forwards compatibility with SEP 11.x GUPs. The above thread did not have an accurate answer. Just clarifying as this has been cofirmed from the Symantec product management team.
A SEP 11.x GUP can distribute content to a SEP 12.1 client as long as they are both communicating to a SEPM 12.1 server. The key is that the SEPM has to be on 12.1 as that is what is distributing content to GUPs. As long as that is on 12.1 version, an 11.x client that is a GUP communicationg back to SEPM 12.1 will successsfully distrubite content to 12.x and 11.x clients. This has been tested with the original 12.1 release.