I'm using cloudflare as CDN provider, unfortunately I'm having issue with the facebook crawler when supposedly someone want to share article from the website and the open graphs don't get loaded properly with message:
Attention Required | cloudflare If you are on personal connection, like at home, you can run an anti-virus on your device to make sure it is not infected with malware.
I'm pretty sure this is because I use cloudflare challenge passage to user before accessing the website.
I've read some of the IPs suggestions like on this thread (What's the IP address range of Facebook's Open Graph crawler?), but the problem with cloudflare is that the CIDR notation for acceptable IP Range are only /16 and /24. But the IP list on this thread suggests like:
31.13.24.0/21
31.13.64.0/18
66.220.144.0/20
69.63.176.0/20
69.171.224.0/19
74.119.76.0/22
103.4.96.0/22
173.252.64.0/18
204.15.20.0/22
What I've done so far is to add this list of IPs with notation /24 at the end, but still not working.
Anyone having similar experience like this and know the work around?
I finally able to solve this by adding /16 CIDR notion for each IP range instead. Example: 31.13.24.0/21 => 31.13.0.0/16. Hope it helps others who need it.