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Azure Vnet Private IP Ranges

I've not from a networking background. I'm data platform solution architecture and data/ai engineer. Since distributed data processing and scale out using containers has come into my world I've decided to bite the bullet and learn IP fundamentals so I can build clusters.

I've been doing lots of training but have a simple and relatively dumb question but finding simple answers to simple questions seems quite hard on the topic networking!

I have 2 Azure VNets for example in my subscription on the same domain does it matter if a subnet on 1 vnet overlaps a subnet on other vnet? Presumably that would only be a problem when they're peered together. Does the vnet ring fence it's private ip ranges?

Solution

  • "I have 2 Azure VNets for example in my subscription on the same domain does it matter if a subnet on 1 vnet overlaps a subnet on other vnet? "*Presumably that would only be a problem when they're peered together."

    To be exact the answer is "NO". It doesn't really matter as long as the particular subnet doesn't require to communicate with another subnet in a different VNET. If you have a plan to configure VNET peering at some point then there are certain best practices that you should have followed to avoid conflicts. However, following are the best practices to implement an enterprise network in Azure.

    1. Start from scratch by documenting your subnets along with subnet mask in each VNET.
    2. There shouldn't be overlapping IP address ranges if your network design contains VNET peering, custom routing, Azure firewall, Azure load balancer etc.
    3. There shouldn't be overlapping IP address ranges if you are planning to implement Site to Site VPN between your azure tenant and on-premises network.

    "Does the vnet ring fence it's private ip ranges?"

    Yes, subenets within a VNET can communicate with each other without any custom routes with the help of default systems routes. But subnets in VNET-A cannot communicate with subnets in VNET-B if there's no VNET peering configured between VNET-A and VNET-B.

    Hope this answer cleared out the doubts.