Introduction to ExpressRoute Gateways

Azure ExpressRoute gateways are a crucial component for establishing private, high-throughput, low-latency connections between your on-premises environments or colocation facilities and Microsoft Azure. They act as the entry point for your traffic into Azure's global network.

Key Benefit: ExpressRoute bypasses the public internet, offering enhanced security, reliability, and predictable performance.

This document provides an in-depth look at ExpressRoute gateway details, including their types, configuration, and best practices for optimal performance and reliability.

ExpressRoute Gateway Types

Azure offers two primary types of ExpressRoute gateways, each designed for different needs:

  • Standard Gateway: Suitable for most enterprise scenarios, offering a balance of performance and cost. It supports a wide range of configurations and connection types.
  • Ultra Performance Gateway: Designed for high-demand scenarios requiring maximum throughput and lowest latency. It offers enhanced performance metrics compared to the Standard gateway.

The choice between Standard and Ultra Performance gateways depends on your specific bandwidth requirements, application latency tolerance, and budget.

Configuration Options

Configuring an ExpressRoute gateway involves several key settings:

Gateway Sizing

Gateway sizing is critical for performance. You can choose from various SKU sizes, impacting the maximum number of BGP routes, connection bandwidth, and aggregate throughput. Common SKUs include:

SKU Name Max Connections Max BGP Routes Throughput (Gbps)
Standard SKU Up to 10 4,000 Up to 1
HighPerformance SKU Up to 20 10,000 Up to 2
UltraPerformance SKU Up to 100 20,000 Up to 10

Note: SKUs and their capabilities may vary and are subject to change. Refer to official Azure documentation for the latest details.

High Availability (HA) and Availability Zones

ExpressRoute gateways are deployed with built-in redundancy. You can also leverage Availability Zones for enhanced resilience. Deploying your gateway in an Availability Zone ensures it is protected from datacenter-level failures within a region.

  • Zone Redundant Gateway: Spans multiple Availability Zones for maximum availability.
  • Zonal Gateway: Deployed within a specific Availability Zone for localized resilience.

BGP Configuration

Border Gateway Protocol (BGP) is used to exchange routing information between your on-premises network and Azure. Key BGP configurations include:

  • ASN (Autonomous System Number): You will use your public or private ASN.
  • BGP Peering: Establishing peering with Azure's BGP routers.
  • Route Maps and Policies: Controlling which routes are advertised and received.

Proper BGP configuration is essential for successful route propagation and network connectivity.

Performance Considerations

Optimizing ExpressRoute gateway performance involves:

  • Choosing the Right SKU: Select a SKU that matches your required bandwidth and route count.
  • Connection Limits: Be aware of the maximum number of connections allowed per gateway SKU.
  • Peering Type: Different peering types (Private, Public, Microsoft) have varying performance characteristics.
  • Number of Routes: A high number of BGP routes can impact control plane performance.

Tip: Regularly review your bandwidth utilization and consider scaling your gateway SKU if you are consistently approaching its limits.

Monitoring and Troubleshooting

Azure provides several tools for monitoring your ExpressRoute gateway and connection:

  • Azure Monitor: For metrics on gateway health, traffic flow, and connection status.
  • ExpressRoute Connection Health: A dedicated blade for troubleshooting connectivity issues.
  • Azure Network Watcher: Tools like connection troubleshoot and IP flow verify can aid in diagnostics.
  • BGP Session Status: Monitor BGP peering status to ensure routes are being exchanged correctly.

Common troubleshooting steps include verifying BGP configurations, checking firewall rules, and ensuring correct IP addressing.

Best Practices

  • Plan for Growth: Choose a gateway SKU that can accommodate future bandwidth and route requirements.
  • Implement Redundancy: Utilize Availability Zones for critical workloads.
  • Secure Your Connection: Implement appropriate security controls and access policies.
  • Regularly Monitor: Proactively monitor gateway performance and connection health.
  • Document Your Configuration: Maintain clear documentation of your ExpressRoute gateway and network setup.
  • Understand BGP: Have a strong understanding of BGP to effectively manage routing.