Hello, i have set up a firewall to block TCP connections for HTTP ports outside Cloudflare and recently i have seen a rather big spike in 521 ’s even though i have whitelisted all the IPv4/6 ranges listed at IP Ranges . Is this list still maintained? [image] (taken via Cloudflare API)

Unusual 521's with firewall whitelists

cloonan June 25, 2019, 4:15pm 2

Yes, it is. There are a few other steps you can take in this Tip, Community Tip - Fixing Error 521: Web server is down. Can you share the domain name here?

Topic		Replies	Views
2weeks haven't solve 521 error with vps Getting Started dash-troubleshooting	2	1991	October 4, 2019
South Africa - cloudflare Error 521: Web server is down DNS & Network firewall , dash-troubleshooting	8	4070	September 15, 2019
When I use cloudflare, sometimes 525 error and 520 error General dns , dash-errors , dash-troubleshooting	5	3881	June 18, 2021
521 error CloudFlare with my websites Getting Started dash-errors , dash-troubleshooting	12	4041	June 8, 2019
Server Down and web down DNS & Network dash-getting-started , dash-errors , dash-troubleshooting	10	3694	April 19, 2019