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Level 7

How does the next hop proxy monitoring work?


we are using a MWG 7.4.2. in explicit proxy mode with two next hop proxies based on squid. I see a lot of alert messages "Next hop proxy x.x.x.x has been marked as down ..." and I would like to find the cause for this.

So does anyone know how this next hop proxy monitoring works? Or can somebody give me a hint where I can find some documentation about this topic. I currently have no idea where I should start looking for errors or problems.

The network interfaces on both the MWG and the squid proxies show no errors, just some dropped packets. The outbound interface of the MWG and the inbound interfaces of the squids are in the same subnet without any firewall or router in between.

In the "Advanced Settings" in "Configuration" -> "Proxies" there is an option called "Status codes of healthy next hop proxy (CONNECT requests)". Does this mean the MWG monitors the HTTP CONNECT request to the next hop proxy and decides based on the HTTP status code the next hop proxy returns whether or not the next hop proxy is healthy?

This option is currently set to "200, 400, 403, 404, 502, 503, 504", searching our squid access logs I did not find any CONNECT requests which did return other HTTP status codes.