Firefox can use your Kerberos credentials for authentication, but you need to specify which domains to communicate with, and using which attributes.
Open Firefox, and type "about:config" in the Address Bar.
In the Search field, type "negotiate".
Ensure the following lines reflect your setup. Replace ".example.com" with your own IPA server's domain, including the preceding period (.):
network.negotiate-auth.trusted-uris .example.com network.negotiate-auth.delegation-uris .example.com network.negotiate-auth.using-native-gsslib true
If you are configuring Firefox on Microsoft
Windows, make the following changes instead:
network.negotiate-auth.trusted-uris .example.com network.auth.use-sspi false
In Firefox, navigate to the IPA server (use the fully-qualified domain name, for example, http://ipaserver.example.com). Ensure that there are no Kerberos authentication errors, and that you can see and interact with the Web interface.