Choose a solution for connecting an on-premises network to Azure

This article compares options for connecting an on-premises network to an Azure Virtual Network (VNet). We provide a reference architecture and a deployable solution for each option.

VPN connection

Use a virtual private network (VPN) to connect your on-premises network with an Azure VNet through an IPSec VPN tunnel.

This architecture is suitable for hybrid applications where the traffic between on-premises hardware and the cloud is likely to be light, or you are willing to trade slightly extended latency for the flexibility and processing power of the cloud.

Benefits

  • Simple to configure.

Challenges

  • Requires an on-premises VPN device.
  • Although Microsoft guarantees 99.9% availability for each VPN Gateway, this SLA only covers the VPN gateway, and not your network connection to the gateway.
  • A VPN connection over Azure VPN Gateway currently supports a maximum of 200 Mbps bandwidth. You may need to partition your Azure virtual network across multiple VPN connections if you expect to exceed this throughput.

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Azure ExpressRoute connection

ExpressRoute connections use a private, dedicated connection through a third-party connectivity provider. The private connection extends your on-premises network into Azure.

This architecture is suitable for hybrid applications running large-scale, mission-critical workloads that require a high degree of scalability.

Benefits

  • Much higher bandwidth available; up to 10 Gbps depending on the connectivity provider.
  • Supports dynamic scaling of bandwidth to help reduce costs during periods of lower demand. However, not all connectivity providers have this option.
  • May allow your organization direct access to national clouds, depending on the connectivity provider.
  • 99.9% availability SLA across the entire connection.

Challenges

  • Can be complex to set up. Creating an ExpressRoute connection requires working with a third-party connectivity provider. The provider is responsible for provisioning the network connection.
  • Requires high-bandwidth routers on-premises.

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ExpressRoute with VPN failover

This options combines the previous two, using ExpressRoute in normal conditions, but failing over to a VPN connection if there is a loss of connectivity in the ExpressRoute circuit.

This architecture is suitable for hybrid applications that need the higher bandwidth of ExpressRoute, and also require highly available network connectivity.

Benefits

  • High availability if the ExpressRoute circuit fails, although the fallback connection is on a lower bandwidth network.

Challenges

  • Complex to configure. You need to set up both a VPN connection and an ExpressRoute circuit.
  • Requires redundant hardware (VPN appliances), and a redundant Azure VPN Gateway connection for which you pay charges.

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