After doing bit of research over the IIS7 failed request log it seems WCF service were failed in the ServiceModel http module
ModuleName="ServiceModel", Notification="AUTHENTICATE_REQUEST", HttpStatus="404", HttpReason="Not Found", HttpSubStatus="0", ErrorCode="The operation completed successfully. (0x0)", ConfigExceptionInfo=""
and the content server’s IIS log showed that the WCF service request were not served. It was clear that the service calls were not routed.
IIS uses httphandlers for serving the incoming request, after disabling svc handlers from the ARR web directory.. request started to route to content servers
Remove the handlers by adding the following to web.config
<handlers> <remove name="svc-ISAPI-2.0" /> <remove name="svc-Integrated-4.0" /> <remove name="svc-ISAPI-4.0_64bit" /> <remove name="svc-ISAPI-4.0_32bit" /> <remove name="svc-Integrated" /> </handlers>