CIDR Notation for my Subnet Ranges

Question

if my Vnet address space ranges are 10.0.0.0/16 and 10.1.0.0/16 for my Vnet peering. What will be my Subnet Ranges for my VNET peering in 172.x.x.x/x series.

Answer 1

@Krishnap , Thank you for reaching out.
Based on my understanding of your question above you have Virtual networks with IP space 10.0.0.0/16 and 10.1.0.0/16 peered and you wish to know what IP space is needed from 172.16.x.x/x series to peer these VNets, please correct me if my understanding is wrong.
In Azure you can use below private IP ranges to create a Virtual Network, you can find more information here.

• 10.0.0.0 - 10.255.255.255 (10/8 prefix)
• 172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
• 192.168.0.0 - 192.168.255.255 (192.168/16 prefix)

You can establish peering between Azure Virtual Networks of any size given that they do not have an overlapping address space. So, in above case you can establish peering between 10.0.0.0/16 and 172.16.0.0/24 OR 172.16.0.0/16 etc. as long as there are no over lapping IP address spaces. The subnets within these network can be of any size greater than /29. As the smallest supported IPv4 subnet is /29.

Just to add a peering is established between two virtual networks. Peerings by themselves aren't transitive. If you create peerings between:

VirtualNetwork1 and VirtualNetwork2

VirtualNetwork2 and VirtualNetwork3

There's no connectivity between VirtualNetwork1 and VirtualNetwork3 through VirtualNetwork2. If you want VirtualNetwork1 and VirtualNetwork3 to directly communicate, you have to create an explicit peering between VirtualNetwork1 and VirtualNetwork3.

You can find more information regarding constraints associated with peering here.

Hope this helps! Please let me know if you have any questions.