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Cloudflare Fundamentals
Cloudflare Docs
Cloudflare Fundamentals
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  1. Products
  2. Cloudflare Fundamentals
  3. Basic tasks
  4. Protect your origin server

Protect your origin server

Your origin server is a physical or virtual machine that is not owned by Cloudflare and hosts your application content (data, webpages, etc.).

Receiving too many requests can be bad for your origin. These requests might increase latency for visitors, incur higher costs — particularly for cloud-based machines — and could knock your application offline.

​​ Secure origin connections

When you secure origin connections, it prevents attackers from discovering and overloading your origin server with requests.

  • DNS:

    1. Proxy records (when possible): Set up proxied (orange-clouded) DNS records to hide your origin IP addresses and provide DDoS protection. As part of this, you should allow Cloudflare IP addresses at your origin to prevent requests from being blocked.
    2. Review DNS-only records: Audit existing DNS-only records (SPF, TXT, and more) to make sure they do not contain origin IP information.
    3. Evaluate mail infrastructure: If possible, do not host a mail service on the same server as the web resource you want to protect, since emails sent to non-existent addresses get bounced back to the attacker and reveal the mail server IP.
    4. Rotate origin IPs: Once onboarded, rotate your origin IPs, as DNS records are in the public domain. Historical records are kept and would contain IP addresses prior to joining Cloudflare.

​​ Application layer

Cloudflare Tunnel (HTTP / WebSockets)

Cloudflare Tunnel connects your resources to Cloudflare without a publicly routable IP address, by creating an outbound-only connections to Cloudflare’s global network.

  • Security: Very secure.
  • Availability: All customers.
  • Challenges: Requires installing the cloudflared daemon on origin server or virtual machine.
HTTP Header Validation

Only allow traffic with specific (and secret) HTTP headers.

  • Security: Moderately secure.
  • Availability: All customers.
  • Challenges:
    • Requires more configuration efforts on application- and server-side to accept those headers.
    • Basic authentication is vulnerable to replay attacks. Because basic authentication does not encrypt user credentials, it is important that traffic always be sent over an encrypted SSL session.
    • There might be valid use cases for a mismatch in SNI / Host headers such as through Page Rules, Load Balancing, or Workers, which all offer HTTP Host Header overrides.
  • Process:
    1. Use Transform rules or Workers to add an HTTP Auth Header.
    2. Configure your origin server to restrict access based on the HTTP Auth Header (or perform HTTP Basic Authentication).
    3. Configure your origin server to restrict access based on the HTTP Host Header. Specifically, only allow requests which contain expected HTTP Host Header values, and reject all other requests.
JSON Web Tokens (JWT) Validation

Only allow traffic with the appropriate JWT.

​​ Transport Layer

Authenticated Origin Pulls

Authenticated Origin Pulls helps ensure requests to your origin server come from the Cloudflare network.

  • Security: Very secure.
  • Availability: All customers.
  • Challenges:
    • Requires Full or Full (strict) encryption modes.
    • Requires more configuration efforts for application and server, such as uploading a certificate and configuring the server to use it.
    • For more strict security, you should upload your own certificate. Although Cloudflare provides you a certificate for easy configuration, this certificate only guarantees that a request is coming from the Cloudflare network.
    • Not scalable for large numbers of origin servers.
Cloudflare Tunnel (SSH / RDP)

Cloudflare Tunnel connects your resources to Cloudflare without a publicly routable IP address, by creating an outbound-only connections to Cloudflare’s global network.

  • Security: Very secure.
  • Availability: All customers.
  • Challenges: Requires installing the cloudflared daemon on origin server or virtual machine.

​​ Network Layer

Allowlist Cloudflare IP addresses

Explicitly block all traffic that does not come from Cloudflare IP addresses (or the IP addresses of your trusted partners, vendors, or applications).

  • Security: Moderately secure.
  • Availability: All customers.
  • Challenges:
    • Requires allowlisting Cloudflare IP ranges at your origin server.
    • Vulnerable to IP spoofing.
Cloudflare Network Interconnect

Cloudflare Network Interconnect allows you to connect your network infrastructure directly with Cloudflare – rather than using the public Internet – for a more reliable and secure experience.

  • Security: Very secure.
  • Availability: Enterprise-only.
  • Challenges
    • Requires some networking knowledge.
    • Only applies to some customer use cases.
Cloudflare Aegis

Cloudflare Aegis prevents external connections by providing dedicated egress IP addresses.

  • Security: Very secure.
  • Availability: Enterprise-only.
  • Challenges: Requires network-level firewall policies.

​​ Monitor origin health

For passive monitoring, create notifications for Origin Error Rate Alerts to receive alerts when your origin returns 5xx codes above a configurable threshold and Passive Origin Monitoring to see when Cloudflare is unable to reach your origin for a few minutes.

For more active monitoring, set up standalone health checks for your origin.

​​ Zero Downtime Failover

If you have another A or AAAA record in your Cloudflare DNS or your Cloudflare Load Balancer provides another origin in the same pool, Zero-Downtime Failover automatically retries requests to your origin even before a Load Balancing decision is made.

Zero-downtime failover will trigger a single retry only if there is another healthy origin in the origin pool and a 521, 522, or 523 error code is occuring. No other error codes will trigger a zero-downtime failover operation.

​​ Reduce origin traffic

​​ Block traffic

For more details, refer to Secure your website.

​​ Increase caching

The cache stores data from your application (webpages, etc.) at Cloudflare data centers around the world, which reduces the number of requests sent to your origin server.

​​ Distribute traffic

To randomly distribute traffic across multiple servers, set up multiple DNS records.

For more fine-grained control over traffic distribution — including automatic failover, intelligent routing, and more — set up our add-on load balancing service.


To protect specific endpoints from being overwhelmed by traffic spikes, set up a waiting room.