This section describes how to modify custom firewall rules.

To modify local firewall rules, edit the following file: /etc/iptables/rules.v4

Important: Add only targeted rules for addresses and ports. Do NOT add blanket drop or accept rules. VCG will append its own rules to the table and, because the rules are evaluated in order, that may prevent Gateway software from functioning properly.
-A INPUT -p udp -m udp --source --dport 161 -m comment --comment "allow SNMP port" -j ACCEPT 
Restart iptables service:
service iptables-persistent restart
service vc_process_monitor restart