How failover should work in IIS cluster with Application Request Routing?

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http://serverfault.com – I have set up several servers with IIS and connected them to the load balancer - server with installed IIS Application Request Routing. I have created a server farm and added two servers. Then I stopped IIS on the first server and tried to open my web site. It returned me an error: 502 - Web server received an invalid response while acting as a gateway or proxy server. But if instead of stopping IIS I shut down the first server, I'm getting a response from the next server which is online. The question is, what the expected behaviour should be for failover with ARR, should it switch me to the (HowTos)