---
title: "Clients cannot log in with NT logon plug-in because the domain is unavailable"
slug: "clients-cannot-log-in-with-nt-logon-plug-in-because-the-domain-is-unavailable"
updated: 2024-04-01T13:50:14Z
published: 2024-04-01T13:50:14Z
canonical: "kb.pharos.com/clients-cannot-log-in-with-nt-logon-plug-in-because-the-domain-is-unavailable"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://kb.pharos.com/llms.txt
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# Clients cannot log in with NT logon plug-in because the domain is unavailable

When clients attempt to log on using the NT logon plug-in, they may be refused with a message saying the domain controller is unavailable. This may also be accompanied by unusual Kerberos errors in the event log, including a mention of KDC_ERR_BADOPTION.

---

This can occur due to the emulation of NT4-style domains in a Windows 2000 or later Active Directory domain if the delegated NT4 authentication system is unavailable or cannot contact the AD domain controllers.

A good workaround is to switch to the Pharos Active Directory LDAP plug-in and bypass the NT4 system. Contact Pharos Support to obtain this plug-in.

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