This is happening for the past 2 days.

I have a web application running on port 80.

When I create a new web application for My Site on port 8080, my port 80 web app stops working and shows "500 internal server error"

I found out that it's because the new My Site web app makes changes in web.config which causes the web app on port 80 to stop working.

I created My Site web app twice and both times this happened. Why is this happening?

Here's more detail about my setup.
I have two WFEs.

WFE1 = WFE2 =

Both are being load balanced using following:

mylb =

When I created first web application on port 80 I gave the host header as "mylb" which is name of my load balancer with IP as mentioned above.

So basically I can access my first web app as follows which is fine:


Then first time I created 2nd web app for My Site on port 8080 but I didn't give any host header so it used the default computer name for that web app. This caused my first web app to stop working which turns out was because of changes in web.config done by My Site web app.

Then I restored web.config from backup and 1st web app started working.

Then I created My Site web app again and this time I entered "mylb" as host header with port 8080 but again same problem occured so I had to restore web.config again to make 1st web app work.

How do I create new web app for My Site? Can I create it on same port i.e. 80 rather than 8080? If yes then do I need a different host header name which will basically be an A record in DNS?

  • Are you sure you changed both the Host Header & URL with the port numbers when you create the MySite host?
    – James Love
    Nov 9, 2013 at 19:59
  • Check the bindings in IIS.
    – Mike
    Nov 9, 2013 at 22:35
  • @JamesLove I am using same host header for both web applications but different port number. May be this is the problem? Nov 10, 2013 at 5:46
  • @Mike I have edited my comments and gave more detail. Nov 10, 2013 at 6:04
  • 1
    And that host header will be an A record with same IP as previous host header right!? Nov 11, 2013 at 6:44

2 Answers 2


I created MySite again with different host header but same problem. I had already taken web.config backup so I simply restored it and now both web applications are working.


If you do not want to mess around with host headers and the like, the other thing you could do is setup another IP address for each web front end for MySites and another IP address for DNS and the load balanced route between them. The basic process is as follows:

  1. Plan and provision the new IP addresses
  2. Assign additional IP addresses to each web front end
  3. Update the IIS bindings on each web front end
  4. Create a new DNS A record for your MySite web application
  5. Setup a new load balanced route for MySites using the web front ends' new IP addresses

If you would like a little more detail than that, read on.

In your example you had the following:

  • WFE1:
  • WFE2:
  • Load Balancer:

These IP address would remain the same for your default web application running on port 80 (whether it is your intranet, website, or whatever). Let's say we plan out and create three new addresses for MySites in particular:

  • WFE1:
  • WFE2:
  • Load Balancer:

In order to add the additional address on each web front end you would do the following:

  1. Open Network Connections
  2. Right click on the connection and select Properties
  3. Select "Internet Protocol Version 4 (TCP/IPv4)" and click on the Properties
  4. Click the Advanced button
  5. Under IP Address click Add
  6. Add your IP address and subnet mask (in our example this would be for WFE1 and for WFE2)
  7. Click Ok

Once the IP addresses have been added to each server, you would go into IIS and change the bindings for your MySite application. Under the IP address section, select the IP address appropriate for each server (which you configured in the previous section), enter the port number (in your case 80), and enter the host name of your MySites web application (e.g. mysite.domain.com). Once this has been done on each web front end, you would go into DNS and add an A record for your MySite web application to be used by your load balancer. In our example, you would set an A record for mysite.domain.com to point to Lastly, add a new route in your load balancer to point the traffic to your web front ends. In our example we would setup the address to pass the load off to and

That should be about it. From there you can test your sites and verify that everything is setup properly. Admittedly, this is a little more work than your current setup but it does allow you to compartmentalize your web applications as well as the ability to take down one route in your load balancer without affecting the traffic on the other routes.

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