I've attempted to create an Azure virtual network using the Classic implementation. This is because I needed the virtual network gateway to handle both site to site and point to site connections. A VPN connection to an on premises network requires me to use a specific Azure address space 10.200.10.10.
I've created the local network connection using the address space above and the IP address to the on premises VPN device. Default subnet is using starting IP 10.200.10.10 CIDR /24 and usable address range 10.200.10.4 - 10.200.10.254. My Gateway subnet is using starting IP 10.200.11.0 CIDR /29 and usable address range 10.200.11.4 - 10.200.11.6. The local network connection is using starting IP 10.200.12.0 CIDR /24 and usable address range 10.200.12.4 - 10.200.12.254.
However, when I attempt to create a site to site connection on my Azure Gateway, I receive the following:
IP address prefix is not valid '10.200.10.0/27' on local site or virtual network MyNetwork
What adjustments are needed in order to use 10.200.10.10 address space to connect to the on premises VPN?
Update: The address space is 10.200.10.10/16.