What is the most Domains you have seen in a single forest?

Some of the microsoft study material for the MCITP etc shows example companies with 8-10 domains.

This got me thinking, I've worked for several large companies over the years and I only recall some of them having more than a single domain.

The 2 largest companies I worked for, I only recall a single domain being there however I am sure there would of been more, I was just unaware because I worked on migration projects and didn't really do much in the way of System Administration.

Find more posts tagged with

SAVE $250 on Your Boot Camp — Use Code "EXAM26"

Exclusively for TechExams members for Infosec Boot Camps starting before April 30, 2026

View Boot Camps

Comments

Qord

We have 6 where I work. We have 5 different organizations that fall under one umbrella organization, so each has their own domain and the overseeing body has their own as well.

jmritenour

If you're including subdomains, I've seen an AD environment with about 20 total domains. This company was really tight with their security, and very highly segmented.

discount81

jmritenour wrote: »

If you're including subdomains, I've seen an AD environment with about 20 total domains. This company was really tight with their security, and very highly segmented.

Were you an enterprise admin, if so how many day to day problems did you encounter just purely in replication ?

I forgot about a large global pharmaceutical company I worked for that had extremely tight security, there was probably 50+ domains there.
I was only desktop support back then so aside from resetting the odd password I wasn't in AD much.

the_Grinch

We did work for a company where they had brought companies and had to show they were separate. So while they had one helpdesk (and us) they actually have 3 domains, all their equipment was co-located in the same building, but different racks. Finally, separate email accounts.

jmritenour

discount81 wrote: »

Were you an enterprise admin, if so how many day to day problems did you encounter just purely in replication ?

It was a customer, they were pretty restrictive about what rights they gave on their domain, and I only got called in when there was a problem. As far as replication issues - not as many as you'd think. Granted, they were pretty light on universal groups and cross domain shares, but most of the problems came from shaky site links.

NinjaBoy

The first organisation that I worked for had (and still has) 3 within the same forest. Now a days, as my department and I support multiple organisations, the max is two.

N2IT

3-4

Different regions globally

DevilWAH

includinf sub domains have seen some with very large numbers, many globle compinies a highly segmented so 10+ is not at all uncommon

bdub

I did help desk for an MSP whose model was to migrate their clients domains to their forest. They had a single forest with probably 50+ sub domains. Thats the most sub domains I have seen.