AWS Certified SysOps Administrator – Associate (legacy) — Question 570

A user has configured ELB with a TCP listener at ELB as well as on the back-end instances. The user wants to enable a proxy protocol to capture the source and destination IP information in the header. Which of the below mentioned statements helps the user understand a proxy protocol with TCP configuration?

Answer options

• A. If the end user is requesting behind a proxy server then the user should not enable a proxy protocol on ELB
• B. ELB does not support a proxy protocol when it is listening on both the load balancer and the back-end instances
• C. Whether the end user is requesting from a proxy server or directly, it does not make a difference for the proxy protocol
• D. If the end user is requesting behind the proxy, then the user should add the ג€isproxyג€ flag to the ELB Configuration

Correct answer: A

Explanation

Proxy Protocol adds a header containing connection information, such as source and destination IPs, to the TCP request. If the client is already routing requests through an external proxy server that appends its own Proxy Protocol header, enabling it on the ELB will result in duplicate headers, which can corrupt the request format on the backend. Thus, Proxy Protocol should not be enabled on the ELB if an external proxy is already handling the connection.