A Wide Area Network (WAN) connects devices, sites, and networks across a broad geographic area – cities, regions, or continents – rather than a single building or campus. Branch offices, data centers, and clouds reach each other over WAN links such as broadband internet, MPLS, or wireless, typically leased from a service provider.
Key takeaways
- A WAN links sites across cities, regions, or continents over provider circuits.
- LANs connect a single site; WANs connect many sites together.
- Common WAN transport types include MPLS, broadband internet, and LTE/5G.
- SD-WAN adds software control and encryption on top of WAN transport.
- On VOS devices, WAN interfaces are the external links to the internet or sites.
On this page: Why it mattersHow it worksTypesWAN & VersaFAQ
Why is a WAN important?
Every organization with more than one location needs a way to connect those locations, and that is the problem a WAN solves. A LAN covers a single building; the moment an organization adds a second office, a data center, or a cloud presence, it needs a WAN to link them with shared routing and security.
WANs matter because they are the foundation the rest of enterprise networking runs on – application performance, security enforcement, and disaster recovery depend on how well the WAN moves traffic between sites. Bandwidth was historically expensive and inflexible, which pushed organizations toward architectures such as SD-WAN that combine cheaper links instead of one costly dedicated circuit.
What is a WAN?
A WAN is a network that spans multiple physical locations, connecting routers, switches, and end systems that are not on the same local network. Unlike a LAN, which an organization typically owns and cables end-to-end, a WAN usually crosses infrastructure it does not own – a provider’s fiber, a carrier’s radio network, or the public internet – so WAN links are purchased as a circuit or subscription rather than built in-house.
A WAN introduces variables a LAN does not have: distance-driven latency, provider-dependent availability, and per-link cost limits. Most sites terminate two or more WAN links for redundancy, and the software that decides which link carries which traffic is the basis of SD-WAN.
Types of WAN links
WANs are built from a mix of transport types with different cost, performance, and availability. MPLS is a provider-managed private circuit with predictable performance and service-level guarantees – historically the default for mission-critical traffic, at a premium price. Broadband internet (cable, fiber, or DSL) is inexpensive and widely available, making it the workhorse transport for modern SD-WAN. Wireless WAN (LTE/5G) provides connectivity independent of wired infrastructure, often used as a backup path. Metro Ethernet and satellite cover high-bandwidth metro sites and remote locations with no terrestrial option.
Most sites combine two or more types – MPLS paired with broadband – so one provider outage does not take the site offline.
WAN & Versa
On a VOS (Versa Operating System) edge device, the WAN side of a deployment is made up of one or more WAN interfaces – the external connections used to reach the internet or remote sites, distinct from the device’s LAN interfaces. A VOS device supports up to 15 WAN links per tenant per device on Release 22.1.1 and later (8 on Release 21.2 and earlier), each assigned a circuit-media type – Ethernet, DSL, or LTE.
Versa’s Secure SD-WAN solution is built around this reality: branches terminate multiple WAN transports on one or two CPE devices, and SD-WAN policy decides which link carries traffic based on live SLA measurements. The Versa SD-WAN design guide covers branch WAN topologies and failover.
Frequently asked questions
What is the difference between a WAN and a LAN?
A LAN (local area network) connects devices within a single building, usually owned and cabled end-to-end by the organization. A WAN connects multiple LANs across cities, regions, or continents over links – MPLS, broadband, or wireless – leased from a provider.
What is the difference between a WAN and SD-WAN?
A WAN is the underlying transport – the physical links connecting sites, whether MPLS, broadband, or wireless. SD-WAN is a software layer on top of that transport, steering traffic across the available links based on application needs and real-time performance instead of static routing.
What are the most common types of WAN links?
The most common types are MPLS (private, provider-managed circuits with guaranteed performance), broadband internet (cable, fiber, or DSL – inexpensive and widely available), and wireless WAN (LTE/5G). Enterprise sites typically combine two or more of these for redundancy and cost optimization.
Why is MPLS still used if broadband internet is cheaper?
MPLS offers provider-guaranteed performance – predictable latency, jitter, and loss – that the public internet cannot contractually promise. Some organizations still route latency-sensitive or compliance-bound traffic over MPLS circuits while shifting general-purpose traffic to cheaper broadband links, all governed by the same SD-WAN policy.
How many WAN links can a Versa VOS device support?
A VOS edge device supports up to 15 WAN links per tenant per device on Release 22.1.1 and later, or 8 links per tenant per device on Release 21.2 and earlier. Each link is assigned its own circuit-media type and forwarding priority.
More on WAN
If you want to learn more, these are sources we trust.
| NIST: Wide area network |
|---|
| NIST’s standards definition of a wide area network, drawn from federal networking and security guidance. |
Related terms
If you’re reading about WAN, these are worth looking at next.
| SD-WAN | Branch | Path |
|---|---|---|
| The software layer that steers traffic intelligently across WAN links instead of relying on static routing. | A branch is a site connected over the WAN to a headend or other branches, typically running a VOS edge device. | The end-to-end route between two branches, built from the WAN circuits at each end of the connection. |