Hello,
* Moved the Thread to SEP 11.x Forums for Better Visibility as the Issue seems to be related to Firewall and not SNAC.
Firewall rules control how the client protects the client computer from malicious inbound traffic and applications, in addition to malicious outbound traffic. Firewall rules can make the computer invisible to others on the Internet, protect remote users from hacker attacks, and prevent hackers from gaining backdoor access to the corporate network through these computers.
Smart traffic filters allow the specific types of traffic that are required on most networks such as DHCP, DNS, and WINS. Examples of traffic and stealth settings that enable additional traffic features are driver-level protection, NetBIOS protection, token ring traffic, DNS reverse lookup, and stealth mode settings. In general, a firewall rule describes the conditions in which a network connection may be allowed or denied.
Understanding the Smart Traffic Filters in Symantec Endpoint Protection 11.0
http://www.symantec.com/docs/TECH148648
Enabling Smart traffic filtering
http://www.symantec.com/docs/HOWTO27095
Adding a new firewall rule
http://www.symantec.com/docs/HOWTO55404
To add more:
How the firewall works
http://www.symantec.com/docs/HOWTO16290
About firewall rules and stateful inspection
http://www.symantec.com/docs/HOWTO16288
About the rule processing order
http://www.symantec.com/docs/HOWTO27107
Configuring the Symantec Endpoint Protection Firewall to filter traffic based on whether its source/destination is from a particular domain
http://www.symantec.com/docs/TECH131681
Hope that helps!!