You can find cloudflare IP range at

https://www.cloudflare.com/ips/

To only allow https traffic from CloudFlare IP ranges, run

iptables -A INPUT -s 103.21.244.0/22 -p tcp --dport https -j ACCEPT
iptables -A INPUT -s 103.22.200.0/22 -p tcp --dport https -j ACCEPT
iptables -A INPUT -s 103.31.4.0/22 -p tcp --dport https -j ACCEPT
iptables -A INPUT -s 104.16.0.0/12 -p tcp --dport https -j ACCEPT
iptables -A INPUT -s 108.162.192.0/18 -p tcp --dport https -j ACCEPT
iptables -A INPUT -s 141.101.64.0/18 -p tcp --dport https -j ACCEPT
iptables -A INPUT -s 162.158.0.0/15 -p tcp --dport https -j ACCEPT
iptables -A INPUT -s 172.64.0.0/13 -p tcp --dport https -j ACCEPT
iptables -A INPUT -s 173.245.48.0/20 -p tcp --dport https -j ACCEPT
iptables -A INPUT -s 188.114.96.0/20 -p tcp --dport https -j ACCEPT
iptables -A INPUT -s 190.93.240.0/20 -p tcp --dport https -j ACCEPT
iptables -A INPUT -s 197.234.240.0/22 -p tcp --dport https -j ACCEPT
iptables -A INPUT -s 198.41.128.0/17 -p tcp --dport https -j ACCEPT
iptables -A INPUT -s 199.27.128.0/21 -p tcp --dport https -j ACCEPT
iptables -A INPUT -p tcp --dport https -j DROP

NOTE: This is for HTTPS, for http, replace –dport https with –dport http

Save the rule with command

On Ubuntu

iptables-save

On CentOS

service iptables save

• cloudflare
• iptables