We have multiple IIS instances spread across remote regional branches. Each IIS instance (v.7.5) is running the same application and authenticates its users with Integrated Authentication (NTLM in the providers list).
A few branches get frequently disconnected from HQ, so that the Domain Controller cannot be reached. When the link to headquarters is down, we observe that some users can still authenticate to the IIS server whereas some others cannot.
The MSFT documentation that we could find on both NTLM and Kerberos authentication does not include information on how these mechanisms (and/or IIS itslef) deal with the situation of temporarily disconnected domain controller. Information is easily available for workstations: a policy setting defines how many logins shall remain cached locally, allowing interactive logons with an offline DC. But what happens for IIS?
- Can authentication occur when the DC is unavailable?
- If yes, what are the requirements?
- Is there some sort of caching involved? (typically: can a domain-member workstation reboot and still access an NTLM-authenticating IIS application if the DC is down?)
Any help or pointers to documentation about this topic would be much appreciated,
kind regards, sb