ExpressRoute

What is Azure ExpressRoute?

Azure ExpressRoute is Microsoft Azure’s service for establishing a dedicated, private network connection between your on-premises infrastructure and Azure, bypassing the public internet entirely. It’s the direct Azure equivalent of AWS Direct Connect (and Google’s Cloud Interconnect): instead of connecting to Azure over an internet-based VPN, you get a private circuit (through a connectivity provider or at an Azure peering location) that delivers consistent high bandwidth, predictable low latency, and greater reliability and security than the public internet can offer. It’s the enterprise choice for hybrid-cloud connectivity where internet-based connections aren’t good enough.

Why organizations use it — the VPN alternative

The reason ExpressRoute exists is the same reason its AWS and GCP counterparts do: the public internet offers no guarantees. An IPsec VPN to Azure is cheap and quick to set up, but it rides the public internet with unpredictable, variable bandwidth and latency and shared-path exposure. ExpressRoute provides a private, dedicated path with the properties enterprises need for demanding hybrid workloads: consistent, high throughput (options up to very high bandwidths for large, steady data movement — replication, backups, big data transfer), predictable low latency (critical for latency-sensitive applications and chatty on-prem-to-cloud communication), reliability (a dedicated circuit rather than best-effort internet), and security/compliance (traffic that never traverses the public internet, satisfying regulatory requirements that forbid sensitive data on public paths). A distinctive Azure detail: ExpressRoute can provide private connectivity not just to your Azure VNets but also, historically, to Microsoft 365 and other Microsoft cloud services over the private circuit (via different “peerings”), which matters for organizations wanting private access to the broader Microsoft cloud, not just Azure IaaS. It connects to your Azure virtual networks via an ExpressRoute gateway, and the private routing is typically established with BGP.

The realities and tradeoffs

ExpressRoute’s tradeoffs mirror Direct Connect’s, and they’re important for architecture and budget decisions. It is more expensive and slower to provision than a VPN — you arrange a circuit through a connectivity provider or at a peering location, incurring port/circuit fees, data charges (metered vs unlimited billing options), and often significant lead time (days to weeks, not minutes) — so it’s justified by genuine requirements for consistent bandwidth, low latency, or private-path compliance, not for small or intermittent connectivity where a VPN is cheaper and far quicker to stand up. Redundancy is essential: for production-critical hybrid connectivity, best practice is redundant ExpressRoute circuits (Azure’s SLA actually requires a redundant configuration) and often a VPN as a backup path — relying on a single circuit is a single point of failure whose loss severs your private connectivity. Many organizations run a hybrid approach: ExpressRoute for the primary high-value private connection and a site-to-site VPN as failover. As with all these services, the honest framing is buy-vs-need: reach for ExpressRoute when the public internet genuinely isn’t good enough (steady large transfers, latency-sensitive apps, compliance), and use a VPN when its lower cost and instant setup suffice. The recurring mistakes: provisioning ExpressRoute (with its cost and lead time) where a VPN would meet the need, deploying a single circuit without redundancy or VPN backup (risking a total connectivity outage), and underestimating the provider coordination and lead time involved in setting it up.

What people get wrong

• Choosing it where a VPN suffices — ExpressRoute’s cost and multi-week provisioning are warranted only by real needs for consistent bandwidth/latency or private-path compliance; a VPN is cheaper and instant for modest needs.
• No redundancy or backup: a single circuit is a single point of failure (Azure’s SLA even requires redundancy) — critical hybrid links need redundant circuits and/or a VPN failover path.
• Underestimating lead time — unlike a VPN you can stand up in minutes, ExpressRoute involves a connectivity provider and physical circuit, often taking days to weeks to provision; plan for it.

Primary source: Azure ExpressRoute documentation