Prompt Users login again and again - [DMZ Servers - Firewall]

Problem: Even though you type in correct username and password, it will prompt the login box again and again. 

Many organizations have DMZ environment to serve External Clients and Vendors. The SharePoint environment is the key to make easy access websites and share. Many cases, internal users also will be having access to these DMZ SharePoint Sites.

Firewall plays the security role to allow authentication between Internal Users and DMZ SharePoint sites. When Firewall is busy or down, it will not authenticated and will not allow Internal Users to access the DMZ SharePoint sites. It behaves the same as like your account was locked.


The Solution is make sure the Firewall is up and running and also make sure, in IIS Manager >> Application Pools, SecurityTokenServiceApplicationPool is started. Also make sure the Account used to run the App Pool is not locked.

If you still see issues, recycle the SecurityTokenServiceApplicationPool

This should fix the issue of Users login Failure or prompt the login box again and again.

There are only few scenarios where users will be unable to login into the site.

1. When User's Account was locked.
2. When Firewall blocks the Authentication request from User.
3. When AD does not respond to authenticate the User Account.