Windows 2008 server & IIS 7 load balancing issue


  • Background:

    We are using MS Windows 2008 server and IIS 7.0 for hosting websites. Multiple sites are hosted on a pair of servers (Server A and Server B) and are listening to specific real server IP address and port number 80 (in case of http site) or 443 (in case of https site)

     We are using the Alteon load balancer. Load balancer is configured to poll the specific service, to check whether status of service is up or down, on the server as:

    <IP address>:<port number>


    When we shut down the website instance in the IIS on say server A, load balances still gets response from the Windows 2008 server A, when it queries the service <IP address>:<port number>. And thus, load balance is not able to figure out if the website went down on server A and keeps on sending requests to the failed server A

     Analysis done so far:

    After a detailed analysis of this issue, we realized that the windows servers are also listening on

     This essentially means that for any <IP addrress>:<port number> query, load balancer will get a response from the server and will treat the service as up. Server is treating as “all IP”


    Problem isolation:

    We have isolated this issue being with Windows 2008 & IIS 7.0 platform as the server has a default binding of <80 or 443> and this makes server to respond to load balancer with a successful response, even if the load balancer is querying both the server with the IP address which does not exist on the server. We have confirmed server is listening on & using the nslookup command.

     We need to figure out how to configure windows 2008 and IIS 7.0 so that when the website instance is shut down on the Server A or server B, failed server should not send successful response to the load balancer.

     Note: There is no default website configured on the server. 

    Any help here is appreciated.

    Thursday, October 01, 2009 7:27 PM