+## Provide NTP service to untrusted clients.
+iptables -A inbound -p udp -j ACCEPT \
+ --source-port 123 --destination-port 123 \
+ -s 172.29.198.0/23
+ip6tables -A inbound -p udp -j ACCEPT \
+ --source-port 123 --destination-port 123 \
+ -s 2001:470:9740::/48
+