Unauthorized 401 status error after deploying custom web application

Very recently while working on custom solution deployment on ms crm 4.0, i encountered a 401 Unauthorized error. The web site was deployed to work On-Premise and was deployed as a new virtual directory within the ISV folder, authentication was set to integrated windows authentication. I recieved the following error though the login credentials used were correct.

Server Error in '/ISV/CustomApplication' Application.
The request failed with HTTP status 401: Unauthorized. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Net.WebException: The request failed with HTTP status 401: Unauthorized.Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace:
[WebException: The request failed with HTTP status 401: Unauthorized.]
System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall) +551137
System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters) +204
Microsoft.Crm.Metadata.MetadataWebService.GetDataSet() +31
Microsoft.Crm.Metadata.DynamicMetadataCacheLoader.LoadDataSetFromWebService(Guid orgId) +301
Microsoft.Crm.Metadata.DynamicMetadataCacheLoader.LoadCacheFromWebService(LoadMasks masks, Guid organizationId) +40
Microsoft.Crm.Metadata.DynamicMetadataCacheFactory.LoadMetadataCache(LoadMethod method, CacheType type, IOrganizationContext context) +418
Microsoft.Crm.Metadata.MetadataCache.LoadCache(IOrganizationContext context) +324
Microsoft.Crm.Metadata.MetadataCache.GetInstance(IOrganizationContext context) +386
Microsoft.Crm.BusinessEntities.BusinessEntityMoniker..ctor(Guid id, String entityName, Guid organizationId) +115
Microsoft.Crm.Caching.UserDataCacheLoader.LoadCacheData(Guid key, ExecutionContext context) +323
Microsoft.Crm.Caching.ObjectModelCacheLoader`2.LoadCacheData(TKey key, IOrganizationContext context) +389
Microsoft.Crm.Caching.BasicCrmCache`2.CreateEntry(TKey key, IOrganizationContext context) +82
Microsoft.Crm.Caching.BasicCrmCache`2.LookupEntry(TKey key, IOrganizationContext context) +108
Microsoft.Crm.BusinessEntities.SecurityLibrary.GetUserInfoInternal(WindowsIdentity identity, IOrganizationContext context, UserAuth& userInfo) +344
Microsoft.Crm.BusinessEntities.SecurityLibrary.GetCallerAndBusinessGuidsFromThread(WindowsIdentity identity, Guid organizationId) +194
Microsoft.Crm.Authentication.CrmWindowsIdentity..ctor(WindowsIdentity innerIdentity, Boolean publishCrmUser, Guid organizationId) +279
Microsoft.Crm.Authentication.WindowsAuthenticationProvider.Authenticate(HttpApplication application) +605
Microsoft.Crm.Authentication.AuthenticationStep.Authenticate(HttpApplication application) +125
Microsoft.Crm.Authentication.AuthenticationPipeline.Authenticate(HttpApplication application) +66
Microsoft.Crm.Authentication.AuthenticationEngine.Execute(Object sender, EventArgs e) +513
System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +92
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +64
Version Information: Microsoft .NET Framework Version:2.0.50727.1433; ASP.NET Version:2.0.50727.1433


The ms crm stack trace showed: LoadDataSetFromWebService() got exception: The request failed with HTTP status 401: Unauthorized.

On searching the web i found out here, that CRM is using an HttpModule for multitenancy. The http module will be called with an anonymous user account and will fail when it's requesting the metadata webservice. So, to make the custom application working, i will need to remove the HttpModule from being loaded. This could be done by making modification the config file of the custom application. Add the remove tags as mentioned below and this would do the trick.

<httpModules>
<remove name ="CrmAuthentication"/>
<remove name ="MapOrg"/>
</httpModules>

This would remove only the specific modules. To remove all the modules you can use a generic clear tag.

<httpModules>
<clear/>
</httpModules>

I hope this helps!!