What does it take to migrate 40,000 devices to a cloud-native environment in a massive, complex enterprise? For most IT leaders, the prospect of moving away from 20 years of legacy infrastructure is enough to cause a sleepless night.

In our latest episode of Entra Chat, we sat down with enterprise veterans Michael Brunker and Prem Kothandapani to deconstruct their recent, massive rollout. They successfully converted nearly 40,000 devices from on-premises Active Directory to Entra Joined in just nine to ten months—all with a lean team of 10–15 people.

Here are the high-stakes lessons they learned from the trenches of modern management.

The “Nuclear Option”: Cleaning Up 20 Years of GPO Debt

One of the most controversial decisions the team made was what they called the “nuclear option” regarding Group Policy Objects (GPOs). Instead of porting over decades of legacy policies that no one fully understood, they chose to start from scratch.

By building a new security baseline from the ground up in Intune, they ensured the new environment was clean, modern, and free from the “stale” configurations that often plague legacy estates.

Killing the “VPN Tax”

For the end user, the primary driver for this migration was a radically improved experience. In a cloud-native world, the dependency on legacy VPN technology disappears.

* Work from Anywhere: Users can sign on and get access without the friction of starting a VPN or worrying about office cabling.

* Security at the Edge: Moving to Entra ID shrinks the attack surface by removing devices as a direct entry point to your core on-prem Active Directory.

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The “Gnarly” Problems: What Breaks First?

Success wasn’t just about the big picture; it was about mastering the “fundamental basic building blocks”. Michael and Prem highlighted several technical hurdles that can derail a migration if not handled early:

* The Proxy Trap: Many organizations fail to update their proxy server allow-lists with the specific Microsoft URLs required for cloud authentication.

* App Authentication: Moving from Kerberos-based device auth to OAuth and modern cloud flows requires rigorous testing across different “personas,” such as front line workers versus corporate office users.

The Secret to Scaling: Small Teams, Big Strategy

Perhaps the most surprising takeaway was that a project of this scale didn’t require an army. By focusing on a “small team” of highly skilled engineers and dedicated communications experts, they maintained momentum and avoided “stop-start” migration fatigue.

Want to hear the full technical breakdown, including how they handled zero-downtime requirements for front line workers?

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About Michael Brunker

Michael Brunker has approaching 40 years in the IT industry and has operated as an enterprise architect across major organizations like BP, Woodside, and Telstra.

LinkedIn - https://www.linkedin.com/in/michaelbrunker/

About Prem Kothandapani

Prem Kothandapani is an EndPoint Architect with over 14 years of experience in endpoint computing and major migrations, having worked at NBN, Australian Unity, and Telstra.

LinkedIn - https://www.linkedin.com/in/premnath-kothandapani-41744153/

📗 Chapters

00:00 Cloud-Native Device Management

02:58 The True Cost of Legacy Infrastructure

07:47 Moving to Modern Management

11:13 The Blueprint for a 40,000 Device Migration

20:07 Handling Complex App Dependencies

28:07 Crafting a Seamless User Migration Experience

33:28 Automating with Graph API and Autopilot

43:09 Avoiding the Co-Management Trap

55:01 The New Starter Experience

57:24 Migration Velocity and Lessons Learned

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