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I'm working on a WordPress site that's served by two lighttpd backends behind an F5 load balancer.

Previously, the site was served by a single lighttpd server behind a nginx reverse proxy, and everything worked fine.

Now, sometimes when sending POST info from the WordPress admin (for instance, when editing general options or editing navigation menus) the site won't reply anything at all. I know that it's receiving the request, because it actually updates the info, but the browser never gets a response.

I'm not seeing anything unusual on the WordPress debug log or the lighttpd logs, so my guess it's that the problem it's related to the load balancer.

Can you think of any reason for this behavior?

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I would start by doing a network capture with a sniffer on the browser machine, load balancer and the two http servers, then compare them.

Check also the load ballancer logs. Enable debugging on it.

If you can not do capture on the load ballancer, you can use a managed switch to record the traffic. On Cisco switches the technology is called SPAN.

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Thanks for your reply! I did a network capture as a client, but it's not telling me that much (perhaps I don't know how to read it), since after the POST all I see are Keep Alive request, some are seem to be ok but then it starts replying "ACKed lost segment"... anyway, I'll check with the team that's managing the server to see if I have better luck – felipelavinz Nov 9 '12 at 14:54

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