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PROXY Protocol

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Problem: backend sees proxy IP, not clientLayer 3 · NetworkIPv4

Client → LB

Src: 93.184.216.34, Dst: LB (203.0.113.10)

LB → Backend

Src: 10.0.0.1 (LB's internal IP), Dst: backend (10.0.0.20)

Problem: backend sees proxy IP, not clientLayer 3 · NetworkIPv4

Client → LB

Src: 93.184.216.34, Dst: LB (203.0.113.10)

LB → Backend

Src: 10.0.0.1 (LB's internal IP), Dst: backend (10.0.0.20)

The problem: all traffic looks like it's from the proxy

When a load balancer forwards a TCP connection, it establishes a new connection to the backend from its own IP. The backend sees the LB's IP, not the real client's.

This breaks: access logs (all show proxy IP), rate limiting (can't limit per real client), GeoIP detection, and security auditing. The client's IP is lost at the TCP level.

Problem: backend sees proxy IP, not clientTCP

Packet structure

Payload

L3

Layer details (click to expand)

3

NetworkIPv4

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Packets in motion — click to inspect:

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