OPNsense VPN sizing
OPNsense VPN Hardware Requirements: WireGuard, IPsec and OpenVPN
VPN hardware sizing is easy to get wrong because the WAN speed, tunnel protocol and actual encrypted traffic are three different numbers. WireGuard, IPsec and OpenVPN take different paths through the system, and cipher choices, MTU, packet size and simultaneous tunnels can change CPU demand. This guide turns an encrypted-throughput target into a conservative OPNsense CPU and memory tier, then shows current firewall appliances that fit those classes.
Quick answer
Size from encrypted throughput and protocol, not ISP speed
WireGuard is the easiest modern starting point when its feature set fits the deployment; OPNsense describes it as fast and more performant than OpenVPN in many cases. IPsec is also capable of high performance. OpenVPN can justify more CPU margin for the same target. A 1Gbps WAN does not require 1Gbps VPN if remote users only consume a fraction of it, while a site-to-site replication tunnel may require most of the link.
Live Amazon hardware
Current OPNsense appliance tiers for VPN workloads
Live listings are grouped by N100, N305 and Core-class firewall appliances. CPU identity must be present in the listing; the catalogue does not assign a VPN Mbps number to a box based on marketing language.
Buying decision
Define the tunnel that matters, then buy CPU margin around it
For modest remote access, N100/N150 can be attractive. N305 is a sensible middle tier for higher WireGuard/IPsec targets or many concurrent services. OpenVPN, large multi-gig site-to-site traffic or VPN plus IDS/IPS can push the decision toward stronger Core hardware. Always test the chosen cipher/protocol on the exact appliance.
Interactive planner
OPNsense VPN Hardware Sizer
Select the VPN protocol and enter encrypted throughput, tunnel count, users and whether inspection also runs. The result returns a conservative CPU/RAM class.
Encrypted throughput is sensitive to protocol, cipher, MTU and traffic mix. The output is a buying tier, not a guaranteed benchmark.
Compatibility checkpoints
VPN sizing inputs that actually change the hardware choice
Protocol
WireGuard, IPsec and OpenVPN have different implementations and performance characteristics. Do not reuse one protocol’s benchmark for another.
Encrypted target
Size from traffic that really enters tunnels, not the full ISP line rate unless the tunnel must carry it.
Concurrency
Many peers and other firewall services create scheduling load even when no single flow is extremely fast.
Inspection overlap
If tunneled or adjacent traffic is also inspected, include Suricata cost in the CPU budget instead of sizing the VPN in isolation.
WAN speed and VPN speed are not the same requirement
A firewall connected to a 2Gbps ISP may only need a few hundred megabits of remote-access VPN because road-warrior clients rarely consume the full line. Conversely, a 1Gbps site-to-site link used for backup replication may spend long periods near the circuit limit. Hardware sizing should follow the encrypted workload, not the marketing speed of the WAN.
List each tunnel type and its peak useful traffic. Separate interactive remote users from bulk site-to-site transfers. This simple inventory often saves money because it reveals that a low-power appliance can handle the realistic VPN requirement even when the WAN itself is much faster.
WireGuard is the natural performance-first remote-access option
OPNsense describes WireGuard as a simple, fast modern VPN and as a considerably more performant alternative to OpenVPN. Its lean design and kernel implementation make it attractive for home and small-business remote access. That does not eliminate CPU cost, but it changes the hardware tier required for a given practical target.
N100-class appliances can be excellent WireGuard boxes for moderate traffic, especially when they are not simultaneously running heavy Suricata inspection. N305 adds room for more peers and background services. If you need multi-gig encrypted throughput, benchmark the exact CPU/NIC combination rather than extrapolating from a single internet result.
IPsec can deliver high performance but configuration matters
OPNsense’s VPN documentation notes that IPsec performance is generally high. StrongSwan supports many proposals and tunnel designs, and those choices affect CPU use. Hardware acceleration availability, negotiated algorithms, packet size and the number of security associations all shape measured performance.
For a site-to-site deployment, test the exact proposal that both endpoints will use. Do not size from an AES benchmark alone because the firewall still handles routing, state tracking and other services around the tunnel. N305 or Core-class CPUs become more attractive as the encrypted target approaches multi-gig rates.
OpenVPN is the protocol most likely to demand extra CPU margin
OpenVPN remains widely used and flexible, but it has historically been more CPU-sensitive than WireGuard and many IPsec configurations. OPNsense has evolved its OpenVPN implementation over time, including work around data-channel offload, so current release behavior should be verified rather than relying on an old benchmark.
If OpenVPN is mandatory, treat high throughput as a stronger CPU requirement. A modern Core i3/i5 can be a safer buy than a low-power N100 when hundreds of megabits or more must be sustained alongside other services. For a handful of users browsing and administering systems, the requirement can be far lower.
Single-flow and aggregate throughput answer different questions
One large site-to-site transfer may expose per-flow or per-core limitations, while many remote users can spread work across multiple connections. A benchmark using eight parallel streams may look excellent but say little about one replication flow. The reverse can also happen when concurrency adds scheduling and memory pressure.
Test the traffic pattern you care about. Use both single-flow and multi-flow measurements when the deployment includes both. Record CPU usage by core so you can see whether the system is constrained by one busy thread or by total processor capacity.
MTU problems can look like slow hardware
WireGuard guidance includes an MTU recommendation and notes that PPPoE can require a smaller value. VPN encapsulation adds headers, and a path with incorrect MTU or broken PMTUD can fragment or stall traffic. Users sometimes replace hardware when the real problem is packet sizing.
Validate MTU before judging CPU performance. Test large transfers, interactive traffic and both directions. If throughput is unexpectedly low while CPU is mostly idle, investigate routing, MTU, NIC errors and upstream shaping before buying a faster processor.
NIC quality still matters inside a VPN firewall
Encryption may be CPU-heavy, but packets still enter and leave through network controllers. A flaky 2.5GbE NIC or constrained virtual interface can limit the tunnel independently of the CPU. OPNsense’s preference for reliable Intel NICs remains relevant in a VPN-focused build.
Match physical link speed to the encrypted target with headroom. A 1GbE interface cannot deliver a 1.5Gbps tunnel no matter how strong the processor is. For 10GbE VPN ambitions, verify PCIe wiring, SFP+/copper media and CPU capability as one end-to-end system.
VPN plus IDS/IPS is a compound workload
A common home-lab design runs WireGuard for remote access and Suricata for network monitoring on the same appliance. These services compete for CPU and memory even if they do not process the exact same packet path in the same way. Sizing each independently can leave no margin when both are busy.
Use the calculator’s IDS overlap flag to move the CPU tier upward. In production, measure both services together during a busy period. If disabling Suricata dramatically changes VPN throughput, you have evidence to tune inspection scope or move to stronger hardware.
User count matters less than traffic pattern until it becomes large
Ten users checking email through a VPN may consume less CPU than one server transferring a large encrypted backup. User count is nevertheless useful because each peer creates state, handshakes and administrative load. At larger scale, concurrency becomes an important capacity signal.
For remote-access sizing, estimate simultaneous active users, not every account ever created. Pair that with expected aggregate Mbps. This prevents oversizing a small office because it has many registered users who are rarely connected at the same time.
Memory is usually not the primary VPN bottleneck
VPN encryption is normally a CPU question before it is a memory question. Eight gigabytes gives a modern OPNsense appliance enough room for the base system and ordinary tunnel workloads. Sixteen gigabytes becomes useful when the same box also runs IDS/IPS, large state tables or many additional packages.
Buying 32GB will not make a slow OpenVPN tunnel faster if a CPU core is saturated. Keep the hardware budget aligned with measured constraints. The processor and network path should receive attention before excessive memory.
Virtualization adds another performance layer
A virtual OPNsense firewall can run VPN services well, but performance also depends on the hypervisor scheduler, virtual NIC type, CPU exposure and whether interfaces are bridged or passed through. Host contention can make a fast CPU look inconsistent because the guest is not always scheduled when it needs to process packets.
Reserve CPU and memory for the firewall, use a supported virtual NIC path, and keep management access outside the guest’s failure domain. Benchmark the VM while other host workloads are active, not only on an idle hypervisor.
Build a repeatable VPN benchmark before deployment day
Create a test endpoint on the far side of the tunnel and measure throughput, latency and CPU using the production protocol and cipher. Test both directions and several stream counts. Then enable the other firewall services that will coexist in production and repeat the test.
Document the result with OPNsense version, MTU and tunnel configuration. This becomes the baseline for later updates. If performance changes, you can identify whether the difference came from software, configuration or network conditions instead of assuming the hardware suddenly became inadequate.
Questions people ask
OPNsense VPN hardware questions
Which VPN is fastest on OPNsense?
OPNsense describes WireGuard as a fast modern VPN and a more performant alternative to OpenVPN in many cases. IPsec can also deliver high performance. Exact results depend on configuration and hardware.
Is N100 enough for OPNsense WireGuard?
It can be an excellent low-power choice for moderate remote-access and site-to-site workloads. Higher targets or heavy concurrent services can justify N305 or Core hardware.
Is N305 better for OpenVPN?
The extra CPU headroom can help, but OpenVPN behavior depends on the OPNsense release, data-channel offload, cipher and traffic pattern. Benchmark the exact setup.
How much RAM does an OPNsense VPN server need?
Eight gigabytes is a practical modern baseline. Sixteen gigabytes is useful when VPN runs with IDS/IPS, larger state tables or other substantial services.
Do I need 10GbE for a 1Gbps VPN?
No. A well-supported 2.5GbE interface already provides link headroom around a 1Gbps encrypted target. Ten-gig networking makes sense for higher aggregate traffic or other routed workloads.
Does AES-NI decide OPNsense VPN performance?
Hardware crypto capabilities can matter for some protocols and ciphers, but they are not a complete throughput predictor. Routing, implementation, packet sizes and other services still contribute.
Can MTU reduce VPN speed?
Yes. Encapsulation changes packet size and incorrect MTU can cause fragmentation or stalls. OPNsense WireGuard guidance includes MTU considerations, including PPPoE.
Should VPN and Suricata run on the same firewall?
They can, but size for simultaneous load and test them together. Heavy inspection can consume CPU headroom that a VPN-only benchmark would otherwise use.
Does user count determine VPN hardware?
Aggregate traffic and protocol are usually more important at small scale. At larger scale, simultaneous peers add connection, handshake and scheduling work and should be included in sizing.
How should I test OPNsense VPN throughput?
Use the production protocol, cipher, MTU and tunnel path; test both directions and single/multiple streams; record CPU per core and latency; then repeat with IDS or other services enabled.
Official references and methodology
Verify current OPNsense and hardware requirements before deployment
VPN sizing is based on the encrypted traffic target, protocol, concurrency and overlapping services. Cloudzat does not publish invented Mbps ratings for retail CPUs. OPNsense’s current descriptions of WireGuard, IPsec and OpenVPN provide protocol context, while live Amazon cards expose only hardware evidence from accepted listings. MTU, cipher, peer behavior and software version should be held constant during validation.
- OPNsense VPN documentation
- OPNsense WireGuard road-warrior guidance
- OPNsense hardware sizing and setup
As an Amazon Associate, Cloudzat may earn from qualifying purchases. Prices, firmware, NIC revisions, link capabilities, appliance configurations and seller terms can change. Verify the exact delivered model and your platform documentation before deployment.