Global VNet to VNet peering is when you connect different virtual networks (VNet) across Azure regions. Once the connectivity is established between the virtual networks, traffic is then privately routed through the Microsoft backbone infrastructure providing a low-latency, high-bandwidth connection between your resources meaning no public internet, gateways or encryption is required in the communication between the virtual networks.
This guide shows you how to peer a VNet in the UK South region with a VNet in East US.
There is a small charge for ingress and egress traffic that use the peering connection.
For your regions pricing see https://azure.microsoft.com/en-us/pricing/details/virtual-network/
In this guide I am using a VNet in the UK South peering it with a VNet in East US with the following details;
VNet - UK South (Address Space: 10.20.0.0/16)
VNet - East US (Address Space: 10.0.0.0/16)
Please be aware, address spaces must not be overlapping for peering to work.
Navigate to one of the virtual networks you want to peer and under settings go to peering, enter 2 logical names (1 for each side) and select the remote VNet. If you require it you can control the directional access here.
Once your details have been verified, click OK then after a minute the peer should be connected to both VNet's
Looking at the effective routes on a network interface of a VM will show the remotes VNet subnet has been added with the next hop set as VNetGlobalPeering.
Providing any local firewalls permit it you should now be able to ping devices across the VNet's.