A10 X-forwarded-for May 2026

If your A10 is configured to append the client IP (the default), the header becomes: X-Forwarded-For: 127.0.0.1, 203.0.113.5

Enter X-Forwarded-For (XFF). This article explores how A10 handles this critical header, how to configure it, and the security pitfalls that come with it. The X-Forwarded-For header is a de facto standard (defined in RFC 7239, though superseded by Forwarded ). Its syntax is a simple comma-separated list: a10 x-forwarded-for

In the CLI:

In the modern data center, the Application Delivery Controller (ADC) sits as the gatekeeper. A10 Networks’ Thunder series is a market leader in this space, performing tasks from server load balancing (SLB) and SSL offload to advanced L7 inspection. If your A10 is configured to append the

A malicious client sends an HTTP request directly to your A10 with a forged header: GET /admin HTTP/1.1 X-Forwarded-For: 127.0.0.1 Its syntax is a simple comma-separated list: In

When configured for L7 load balancing (HTTP mode), the A10 ADC rewrites the HTTP request headers before forwarding the packet to the real server. It typically appends the original client IP address to the existing XFF header.