Changing the Azure Gateway subnet with Express Route

One of the things that I like to do when I start a new Azure Architecture, is what I called an Azure Foundation workshop, where I can validate all the infrastructure configuration, so we can design accordingly. But not always happens on that way.

So, this is the scenario: Costumer has an Express Route setup between their datacenter and Azure. The Express Route terminates on the Core VNet. But the VNet needs to be extended and therefore the subnets (including the Gateway subnet) needs to change.

The rule is, if you need to change the VNet and/or Subnet address that is been used, you CAN’T! So, you need to delete (what you want to change (in this case the Gateway subnet)) and recreate it. So far so good, but in this scenario, we already have an Express Route connection stablish and working to the Gateway Virtual Network.

This is the steps that you should do to accomplish the change:

  1. Disconnect the Gateway from Express Route circuit
  2. Delete the Gateway
  3. Update (or recreate) the Gateway subnet
  4. Recreate the Gateway
  5. Create new connection between Gateway and Express Route circuit

These steps need to happen on both sides, on Azure and on the Datacenter.

I hope this gives you a guidance, if you face this situation.


Marcos Nogueira
Azure MVP
Twitter: @mdnoga

Marcos Nogueira

With more than 18 years experience in Datacenter Architectures, Marcos Nogueira is currently working as a Principal Cloud Solution Architect. He is an expert in Private and Hybrid Cloud, with a focus on Microsoft Azure, Virtualization and System Center. He has worked in several industries, including Aerospace, Transportation, Energy, Manufacturing, Financial Services, Government, Health Care, Telecoms, IT Services, and Gas & Oil in different countries and continents. Marcos was a Canadian MVP in System Center Cloud & Datacenter Managenment and he has +14 years as Microsoft Certified, with more than 100+ certifications (MCT, MCSE, and MCITP, among others). Marcos is also certified in VMware, CompTIA and ITIL v3. He assisted Microsoft in the development of workshops and special events on Private & Hybrid Cloud, Azure, System Center, Windows Server, Hyper-V and as a speaker at several Microsoft TechEd/Ignite and communities events around the world.

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