how to forward ntp traffic to default gateway instead of vpn tunnel

I have a small Raspberry Pi server connected to an openvpn provider, used as a VPN gateway. Almost everything works fine with the following iptables rules: iptables -t nat -A POSTROUTING -o tun0 -j MASQUERADE iptables -A FORWARD -i tun0 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A FORWARD -i eth0 -o tun0 -j ACCEPT However, the VPN provider blocks NTP traffic (udp port 123). How do I make iptables route all NTP traffic via the default gateway (which is 192.168.1.1 on eth0)?