A second office changes how people reach files, applications and the phone system. Staff in different locations need the same access. The network has to carry that work between sites without making people wait.
Three common designs exist. Cost, performance and running effort are the trade-offs.
Site-to-site VPN
A site-to-site VPN builds an encrypted tunnel between the routers at each office, using the public internet as the path. It's the lowest-cost way to join two or three locations.
Pros: Low spend, straightforward to install, encrypts traffic travelling between offices. Cons: Speed follows whatever internet each site already has. Broadband with high latency or jitter can make cloud software and VoIP feel slow across the tunnel.
Best for: Two to three offices that mainly share files, with each site using its own internet connection.
MPLS
MPLS is a private network run by one carrier. Traffic between offices stays off the public internet. The carrier commits to bandwidth, latency and uptime.
Pros: Committed performance, low latency, covered by an SLA, isolated from the public internet. Cons: High cost. You're tied to one carrier. A further site typically takes weeks to provision. Branch offices usually send internet traffic back through headquarters rather than going out locally.
Best for: Organisations that need strict performance and can pay for it. SD-WAN is steadily taking its place.
SD-WAN
Software-Defined Wide Area Network (SD-WAN) sits above the connections you already have. Broadband, a leased line, 4G or 5G can all feed it. The overlay then steers traffic across every available link.
Pros: Combines lower-cost links (broadband, 4G) with premium ones (leased lines). Failover between links happens automatically. Routing can favour critical applications. Each site can reach cloud software directly. New offices join more quickly. Cons: Each site needs an SD-WAN appliance or licence. The first installation is more involved than a basic VPN.
Best for: Three or more sites. Strongest fit where cloud applications and VoIP are in daily use.
How to choose
| Factor | VPN | MPLS | SD-WAN | |---|---|---|---| | Cost | Low | High | Medium | | Performance | Variable | Guaranteed | Adaptive | | Resilience | Single link | Single carrier | Multi-link | | Scalability | Limited | Slow | Fast | | Cloud optimised | No | No | Yes | | Setup time | Hours | Weeks | Days |
Most UK businesses with more than one office will be better served by SD-WAN. It approaches MPLS-level performance for less money. It also uses multiple links and sends cloud traffic out locally.
Why the network matters for automation
Once workflow automation is in place, the path between offices also carries document processing, AI agents and helpdesk traffic. Those services need a stable route to the systems they sit on. Predictive monitoring can flag a degrading link before it interrupts that work.
How Wanzo designs multi-site networks
We review the circuits available at each address and estimate the load each office will put on them. The overlay is then built around that picture. Failover is designed in from the start. The estate is managed from the centre, so a technician isn't required at every site.
Next steps
Send the details of your sites through our contact page. We'll come back with a design and a monthly plan.