Microsoft Azure Virtual Network Services : Reading #4 Intersite Connectivity

Intersite Connectivity Options

Intersite Connectivity

Considerations for Intersite Connections
Azure supports a maximum of 30 VPN tunnels per VPN gateway. Each point-to-site VPN, site-to-site VPN, or VNet-to-VNet VPN counts as one of those VPN tunnels. A single VPN gateway can support up to 128 connections from client computers.
Address spaces must not overlap. Carefully plan the address spaces that you want to use in virtual networks and any connected on-premises networks to avoid IP conflict.
VNet-to-VNet VPNs can connect virtual networks in the same or different Azure subscriptions. Similarly, they can connect virtual networks in the same or different Azure regions.
Redundant tunnels are not supported.
Cloud services cannot span virtual networks, even when those virtual networks are connected with a VPN.
All VPN tunnels to a virtual network share the available bandwidth on the Azure VPN gateway. This includes point-to-site VPNs.
VPN devices must meet certain requirements. About VPN devices for Site-to-Site VPN Gateway connections and a list of compatible third-party VPN devices.

Four type of Intersite connectivity
Point-to-Site VPN
Site-to-Site VPN Connections
VNet-to-VNet Connections
ExpressRoute Connections