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  1. Products
  2. Network
  3. Pseudo IPv4

Pseudo IPv4

Cloudflare customers can use Pseudo IPv4 if their origin web server only understands IPv4 formatted IP addresses (meaning it would not support Cloudflare’s default IPv6 compatibility).

​​ Availability

FreeProBusinessEnterprise

Availability

YesYesYesYes

​​ Background

Some older origin server analytics and fraud detection software expect IP addresses in an IPv4 format and do not support IPv6 addresses.

Pseudo IPv4 uses the  Class E IPv4 address space to provide as many unique IPv4 addresses corresponding to IPv6 addresses as possible.

  • Example Class E IPv4 address: 240.16.0.1
  • Example IPv6 address: 2400:cb00:f00d:dead:beef:1111:2222:3333

​​ Configure Pseudo IPv4

Cloudflare offers three options for configuring Pseudo IPv4:

  • Off: Default value.
  • Add Header: Cloudflare automatically adds the Cf-Pseudo-IPv4 header with a Class E IPv4 address hashed from the original IPv6 address.
  • Overwrite Headers: If Pseudo IPv4 is set to Overwrite Headers - Cloudflare overwrites the existing Cf-Connecting-IP and X-Forwarded-For headers with a pseudo IPv4 address while preserving the real IPv6 address in CF-Connecting-IPv6 header.

To configure Pseudo IPv4:

To change the Pseudo IPv4 setting in the dashboard:

  1. Log in to your Cloudflare account and go to a specific domain.
  2. Go to Network.
  3. For Pseudo IPv4, choose your desired setting.
To change Pseudo IPv4 with the API, send a PATCH request with pseudo_ipv4 as the setting name in the URI path, and the value parameter set to your desired value: "off", "add_header", or "overwrite_header".