AH03507: RemoteIPProxyProtocol: unsupported command 20

Help!
1

I have an HAProxy server on one machine that’s forwarding requests to Apache on 3 other machines using the Proxy Protocol 2.

On the Apache machine the log is being spammed with the following:

[Sun Dec 07 21:22:48.103096 2025] [remoteip:error] [pid 798] [client 10.7.6.107:38562] AH03507: RemoteIPProxyProtocol: unsupported command 20

The relevant Apache configuration is as follows:

Listen *:8088

<VirtualHost *:8088>
	RemoteIPProxyProtocol On
    RemoteIPProxyProtocolExceptions 127.0.0.1
</VirtualHost>

This is the corresponding HAProxy configuration:

backend cdn
	balance roundrobin
    server-template    default-server 3 cdn.pacyworld.com:8088 check resolvers pacydns init-addr none send-proxy-v2

I am running Apache 2.4.65 and HAProxy 3.2.5

2

The question is: does it work or not?

If everything works fine, but your Apache log keeps showing those errors likely some other systems, perhaps a monitoring system is accessing port 8088 on those backends directly without the proxy protocol.

If it doesn’t work, either component may not have the configuration applied fully or is buggy.

3

It does work (at least as far as I can tell). The IP address is from the HAProxy host, and there isn’t anything else running on that machine that would hit the Apache backend.

4

You have posted a correct 5 line snippet of the Apache configuration and a correct 3 line snippet of the haproxy configuration.

Other than saying that this part of the configuration is not wrong, there is really nothing to be done remotely.

Either you provide more information (like the full configuration with private data replaced instead of removed), or your capture the traffic and analyze the proxy protocol traffic.