AD computer disappearing trick

[delstar]

Wazz : Antivirus. Just re-joining it to the domain fixed it, but we want to know what caused it in the first place.

oofki : AD won't add the computer unless a domain admin does it. Netbios has nothing to do with it (as far as I know). None of our systems have software firewalls enabled, and no one outside of our IT department can change the name of the computer (plus, it hasn't been changed since it's been moved into this building)

[phishphreek]

I've had this happen in the past with a bunch of things. DFS subscriptions, computer names, site to site replication subscriptions (NTDS), etc.

For me, It is normally problem with AD replication. During replication, that object becomes "orphaned" and it is moved to the lost and found folder. Have you looked in the "lost and found" container? From there, you can either move them back the the correct place or delete them and recreate them. I tend to just recreate them because I don't know why they were lost to begin with.

Do you have a lot of replication errors or kcc errors? The easiest way I've found to get rid of replication or kcc errors is to demote the AD server with problems, and let that replication take place on all other AD servers. This is normally the time where I'll also get an unsucessful removal of a domain controller and have to use ntdsutil and adsi edit. After all that, I'll normally wait a couple of hours for good measure. I'm on a pretty slow WAN, so I like to be safe... Then I'll rejoin it and let it get all new replica info.

We've had problems like this probably 3 or 4 times since moving from nt4 2000 mixed mode and again after moving to 2000 native. I suspect a couple of the problems were due to some of the AD servers being on different SPs at different times. Since then, I've been very careful to make sure they all have very similar SP and update levels along with configs.