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In my previous post, I talked about splitting our Microsoft Office SharePoint Server (MOSS) 2007 Development environment (DEV) into multiple VMs. What I did not mention, however, is the nasty bug in Windows Update that I encountered along the way.
Before I can explain the bug I first need to describe the environment. The following model shows the important pieces of the environment.
DEV is comprised of five VMs running on a single Virtual Server 2005 host:
ISA Server is used to securely publish the Web applications (in other words, it allows us to access DEV without having to TermServ into the Virtual Server host, launch VMRC, and browse to a site). It also acts as the gateway for the DEV VMs so that they can access other (physical) servers outside DEV (for example, to copy files to or from another server).
Using the Virtual Server Administration Website, I created virtual networks (VLAN1 and VLAN2) to represent the "front-end" and "backend" networks for the MOSS servers.
Also note that in my current customer's environment, you must use a proxy server (PROXY1) in order to access the Internet. Note that PROXY1 is not an ISA Server so I am not using the "firewall chaining" feature in ISA Server. This customer does not use WPAD so you have to manually configure the proxy server and specify port 8088. This is where I discovered the bug in Windows Update...
Since I wanted to allow the DEV VMs to connect to the Internet, I configured the proxy server on each VM (to point to PROXY1) and added a rule on ISA1 to allow outbound HTTP traffic from the internal network (i.e. VLAN1 and VLAN2) to the external network. However, I quickly discovered that this did not work because, as I mentioned earlier, the proxy is configured for port 8088. Therefore I added a new custom protocol to the access rule to allow HTTP on port 8088. Bingo! I could now access the Internet from each VM in DEV.
However, when I browsed to Windows Update, I discovered that while it was able to determine what updates I needed, it was not able to actually download and install the patches. Looking at the logs on ISA1, I noticed many requests on port 80 after approving the installation of the patches. After researching the problem a little, several support incidents indicated that the proxycfg utility needed to be used to get BITS to work with a proxy server. (BITS is used by Windows Update to download -- but not detect -- the patches).
I ran "proxycfg -u" to import my settings from Internet Explorer. However, I still was not able to download the patches. I rebooted (hoping that the BITS would start using the proxy settings). No luck. I even found one SOX article -- which is basically an FAQ created internally based on common SRXs (service requests, a.k.a. support incidents) -- that stated that you need to start a command prompt as LocalSystem (the author creatively recommended using a one-time scheduled task to do this) and running proxycfg there. Well, that may have solved some people's problems but it did not solve mine.
What I discovered is that when ISA1 allows Windows Update to pass requests to PROXY1, then that proxy server receives the request and subsequently returns an error code (since it requires port 8088 to be used). When the error is received by Windows Update, it tries again with a different destination IP (hoping that it can somehow find a Windows Update server). This process repeats for a couple of iterations and then it finally times out (meaning you don't get any patches). Apparently the error returned from PROXY1 when a request comes in on port 80 is not acknowledged by the BITS client as being a "real" problem, so BITS goes ahead and tries again (until it eventually gives up).
The solution that I discovered is that I needed to remove HTTP (port 80) from the access rule on ISA1 (but still allowing port 8088). This way, when Windows Update attempts to download the patches, it receives an "access denied" error from ISA1. The underlying BITS client then proceeds to use the proxy server configuration (i.e. it requests the download on port 8088).
Way more infrastructure than I care for, but definitely an educational experience for me.