Hi,
You can verify through sylink monitor logs.
How to confirm if Clients are receiving Live Update content from Group Update Providers (GUPs)
http://www.symantec.com/business/support/index?page=content&id=TECH97190&locale=en_US
Troubleshooting the Group Update Provider (GUP) in Symantec Endpoint Protection (SEP)
http://www.symantec.com/docs/TECH104539