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. SD-WAN Gateway 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 netfilter service:

service netfilter-persistent restart
service vc_process_monitor restart