Virtual network peering
Virtual network peering enables you to seemlessly connect two Azure virtual networks. Once peered, the virtual networks appear as one, for connectivity purposes. The traffic between virtual machines in the peered virtual networks is routed through the Microsoft backbone infrastructure, much like traffic is routed between virtual machines in the same virtual network, through private IP addresses only.
The benefits of using virtual network peering include:
- Network traffic between peered virtual networks is private. Traffic between the virtual networks is kept on the Microsoft backbone network. No public Internet, gateways, or encryption is required in the communication between the virtual networks.
- A low-latency, high-bandwidth connection between resources in different virtual networks.
- The ability for resources in one virtual network to communicate with resources in a different virtual network, once the virtual networks are peered.
- The ability to transfer data across Azure subscriptions, deployment models, and across Azure regions (preview).
- The ability to peer virtual networks created through the Azure Resource Manager or to peer one virtual network created through Resource Manager to a virtual network created through the classic deployment model. To learn more about Azure deployment models, see Understand Azure deployment models.
- No downtime to resources in either virtual network when creating the peering, or after the peering is created.
Requirements and constraints
Peering virtual networks in the same region is generally available. Peering virtual networks in different regions is currently in preview in US West Central, Canada Central, and US West 2. Before peering virtual networks in different regions, you must first register your subscription for the preview. Attempting to create a peering between virtual networks in different regions fails if you haven't completed registration for the preview.
Virtual network peerings created cross-region may not have the same level of availability and reliability as peerings in a general availability release. Virtual network peerings may have constrained capabilities and may not be available in all Azure regions. For the most up-to-date notifications on availability and status of this feature, check the Azure Virtual Network updates page.
The peered virtual networks must have non-overlapping IP address spaces.
- Address ranges cannot be added to or deleted from the address space of a virtual network once a virtual network is peered with another virtual network. If you need to add address ranges to the address space of a peered virtual network, you must remove the peering, add the address space, and then add the peering again.
- Virtual network peering is between two virtual networks. There is no derived transitive relationship across peerings. For example, if virtualNetworkA is peered with virtualNetworkB, and virtualNetworkB is peered with virtualNetworkC, virtualNetworkA is not peered to virtualNetworkC.
- You can peer virtual networks that exist in two different subscriptions, as long a privileged user (see specific permissions) of both subscriptions authorizes the peering, and the subscriptions are associated to the same Azure Active Directory tenant. You can use a VPN Gateway to connect virtual networks in subscriptions associated to different Active Directory tenants.
- Virtual networks can be peered if both are created through the Resource Manager deployment model or if one virtual network is created through the Resource Manager deployment model and the other is created through the classic deployment model. Virtual networks created through the classic deployment model cannot be peered to each other, however. You can use a VPN Gateway to connect virtual networks created through the classic deployment model.
Though the communication between virtual machines in peered virtual networks has no additional bandwidth restrictions, there is a maximum network bandwidth depending on the virtual machine size that still applies. To learn more about maximum network bandwidth for different virtual machine sizes, read the Windows or Linux virtual machine sizes articles.
After virtual networks are peered, resources in either virtual network can directly connect with resources in the peered virtual network.
The network latency between virtual machines in peered virtual networks in the same region is the same as the latency within a single virtual network. The network throughput is based on the bandwidth that's allowed for the virtual machine, proportionate to its size. There isn't any additional restriction on bandwidth within the peering.
The traffic between virtual machines in peered virtual networks is routed directly through the Microsoft backbone infrastructure, not through a gateway or over the public Internet.
Virtual machines in a virtual network can access the internal load-balancer in the peered virtual network in the same region. Support for internal load balancer does not extend across globally peered virtual networks (preview). The general availability release of global virtual network peering will have support for internal load balancer.
Network security groups can be applied in either virtual network to block access to other virtual networks or subnets, if desired. When configuring virtual network peering, you can either open or close the network security group rules between the virtual networks. If you open full connectivity between peered virtual networks (which is the default option), you can apply network security groups to specific subnets or virtual machines to block or deny specific access. To learn more about network security groups, see Network security groups overview.
You can configure user-defined routes that point to virtual machines in peered virtual networks as the next hop IP address, or to virtual network gateways, to enable service chaining. Service chaining enables you to direct traffic from one virtual network to a virtual appliance, or virtual network gateway, in a peered virtual network, through user-defined routes.
You can deploy hub-and-spoke networks, where the hub virtual network can host infrastructure components such as a network virtual appliance or VPN gateway. All the spoke virtual networks can then peer with the hub virtual network. Traffic can flow through network virtual appliances or VPN gateways in the hub virtual network.
Virtual network peering enables the next hop in a user-defined route to be the IP address of a virtual machine in the peered virtual network, or a VPN gateway. You cannot however, route between virtual networks with a user-defined route specifying an ExpressRoute gateway as the next hop type. To learn more about user-defined routes, see User-defined routes overview. To learn how to create a hub and spoke network topology, see hub and spoke network topology.
Gateways and on-premises connectivity
Each virtual network, regardless of whether it is peered with another virtual network, can still have its own gateway and use it to connect to an on-premises network. You can also configure virtual network-to-virtual network connections by using gateways, even though the virtual networks are peered.
When both options for virtual network interconnectivity are configured, the traffic between the virtual networks flows through the peering configuration (that is, through the Azure backbone).
When virtual networks are peered in the same region, you can also configure the gateway in the peered virtual network as a transit point to an on-premises network. In this case, the virtual network that is using a remote gateway cannot have its own gateway. A virtual network can have only one gateway. The gateway can be either a local or remote gateway (in the peered virtual network), as shown in the following picture:
Gateway transit is not supported in the peering relationship between virtual networks created through different deployment models or different regions. Both virtual networks in the peering relationship must have been created through Resource Manager and must be in the same region for gateway transit to work. Globally peered virtual networks do not currently support gateway transit.
When the virtual networks that are sharing a single Azure ExpressRoute connection are peered, the traffic between them goes through the peering relationship (that is, through the Azure backbone network). You can still use local gateways in each virtual network to connect to the on-premises circuit. Alternatively, you can use a shared gateway and configure transit for on-premises connectivity.
Virtual network peering is a privileged operation. It’s a separate function under the VirtualNetworks namespace. A user can be given specific rights to authorize peering. A user who has read-write access to the virtual network inherits these rights automatically.
A user who is either an admin or a privileged user of the peering ability can initiate a peering operation on another virtual network. The minimum level of permission required is Network Contributor. If there is a matching request for peering on the other side, and if other requirements are met, the peering is established.
For example, if you were peering virtual networks named myVirtualNetworkA and myVirtualNetworkB, your account must be assigned the following minimum role or permissions for each virtual network:
|Virtual network||Deployment model||Role||Permissions|
|myVirtualNetworkA||Resource Manager||Network Contributor||Microsoft.Network/virtualNetworks/virtualNetworkPeerings/write|
|Classic||Classic Network Contributor||N/A|
|myVirtualNetworkB||Resource Manager||Network Contributor||Microsoft.Network/virtualNetworks/peer|
|Classic||Classic Network Contributor||Microsoft.ClassicNetwork/virtualNetworks/peer|
When peering two virtual networks created through Resource Manager, a peering must be configured for each virtual network in the peering. You can monitor the status of your peering connection. The peering status is one of the following states:
- Initiated: The state shown when you create the peering from the first virtual network to the second virtual network.
- Connected: The state show once you've created the peering from the second virtual network to the first virtual network. The peering state for the first virtual network changes from Initiated to Connected. A virtual network peering is not successfully established until the state for both virtual network peerings is Connected.
- Disconnected: The state shown if a peering from one virtual network to another is deleted after a peering is established between two virtual networks.
To confirm a virtual network peering, you can check effective routes for a network interface in any subnet in a virtual network. If a virtual network peering exists, all subnets within the virtual network have routes with next hop type VNet peering, for each address space in each peered virtual network.
You can also troubleshoot connectivity to a virtual machine in a peered virtual network using Network Watcher's connectivity check. Connectivity check lets you see how traffic is routed from a source virtual machine's network interface to a destination virtual machine's network interface.
There are limits on the number of peerings that are allowed for a single virtual network. For details, see Azure networking limits.
There is a nominal charge for ingress and egress traffic that utilizes a virtual network peering connection. For more information, see the pricing page.
Complete a virtual network peering tutorial. A virtual network peering is created between virtual networks created through the same, or different deployment models that exist in the same, or different subscriptions. Complete a tutorial for one of the following scenarios:
Azure deployment model Subscription Both Resource Manager Same Different One Resource Manager, one classic Same Different
Learn how to create a hub and spoke network topology.
- Learn about all virtual network peering settings and how to change them