OPNsense Hardware Requirements: CPU, RAM, Storage & NICs

Quick Answer

OPNsense itself does not require high-end hardware.

According to the current official OPNsense hardware requirements, the minimum configuration is a 1 GHz dual-core CPU with 3 GB of RAM, while the recommended configuration is a 1.5 GHz multi-core CPU, 8 GB of RAM, and a 120 GB SSD.

However, these figures should only be regarded as a starting point for reference.

The actual hardware you need largely depends on:

• Internet speed
• VPN trafficI
• DS/IPS
• Number of users and connections
• Number of VLANs
• Additional plugins
• Whether OPNsense runs on bare metal or inside a virtual machine

If you are building a new firewall for a home or small office, it is more practical to size the hardware around the actual workload rather than simply meeting the minimum system requirements.

1. Official OPNsense Hardware Requirements

According to the official OPNsense Hardware Sizing & Setup documentation, the hardware recommendations are currently categorized as minimum, reasonable, and recommended configurations.

OPNsense positions the recommended configuration as suitable for running its standard features in most use cases.

However, that does not mean every firewall with 8 GB of RAM will deliver the same performance.

A router running only a small number of firewall rules has very different hardware requirements from a system handling VPN traffic, intrusion prevention, traffic analytics, and a large number of concurrent connections.

2. How Much CPU Does OPNsense Need?

For basic OPNsense routing, CPU requirements are relatively modest.

Light workloads usually include:

• NAT / DHCP / DNS
• Basic firewall rules
• VLAN / Multi-WAN
• Basic traffic monitoring

Modern low-power x86 processors can generally handle these tasks without difficulty.

CPU requirements increase when OPNsense needs to perform more processing on each packet.

OPNsense also notes that intrusion detection, caching services, and environments with large numbers of simultaneous users or connections can significantly affect hardware requirements.

Practical CPU Selection

For a broader comparison across N100, N150, N305, and N355, see our CWWK N100 vs N150 vs N305 vs N355 guide.

The key point is:

WAN speed alone should not determine your CPU choice.

Two OPNsense systems using the same 1Gbps internet connection may need very different processors if one only handles routing while the other also runs VPN and traffic inspection.

3. How Much RAM Does OPNsense Need?

The current official recommended configuration for OPNsense is 8 GB of RAM, mainly to leave enough capacity for most standard features.

For a dedicated home firewall, actual RAM usage may remain relatively modest.

However, the following features can increase memory requirements:

• IDS/IPS
• Network analytics
• Large state tables
• Additional plugins
• Extensive logging
• Virtualization

The OPNsense state table also consumes memory, so environments with very large numbers of simultaneous connections naturally require more RAM.

When configuring a new OPNsense firewall, we generally consider:

8 GB of RAM

a practical starting point rather than building a new system around the minimum requirement just to save a small amount of cost.

If OPNsense runs under Proxmox, you also need to account for the memory used by:

• The firewall VM
• The Proxmox host
• Other VMs / containers

4. How Much Storage Does OPNsense Need?

For firewall performance, storage is generally less important than the CPU and NICs.

The current recommended OPNsense configuration uses a 120 GB SSD, while the reasonable configuration specifies a 40 GB SSD.

For a new firewall appliance, an SSD is generally preferable to using removable flash media as the primary long-term storage device.

The goal is not to buy the largest SSD available. You simply need enough capacity for:

• Operating system
• Updates
• Logs
• Additional services

5. Network Interfaces Matter as Much as the CPU

All firewall traffic ultimately passes through the network interfaces.

NIC stability and driver compatibility are therefore important.

OPNsense is based on FreeBSD, and its official hardware documentation specifically notes that Intel network interfaces generally provide good reliability while handling high throughput with relatively low CPU overhead.

When choosing an OPNsense appliance, check:

• NIC chipset
• Number of Ethernet ports
• 2.5GbE / 10GbE
• FreeBSD driver compatibility
• Whether SFP+ is required

For most home networks, multiple 2.5GbE ports are a practical starting point.

If you need to connect to a 10GbE switch, NAS, server, or high-speed backbone, then 10GbE becomes more relevant.

6. How Should You Size Hardware for Different OPNsense Workloads?

7. What About Virtualized OPNsense?

OPNsense also provides official guidance for virtual and cloud-based installations, including KVM-based environments.

Its virtual machine guidance specifies at least:

• 3 GB RAM
• At least 8 GB of virtual disk space recommended

However, these requirements apply only to the OPNsense guest VM itself.

If you use Proxmox, the host also needs additional resources for:

• Proxmox
• Other VMs
• Containers
• DNS
• Monitoring
• Other services

Once OPNsense is virtualized, the question is no longer:

How much hardware does OPNsense need?

It becomes:

How much hardware do OPNsense and the entire virtualization host need together?

Related Guide: Bare Metal vs Virtualized Firewall

FAQ

Is 4 GB of RAM Enough for OPNsense?

Yes, OPNsense can run with 4 GB of RAM, which it lists as a reasonable configuration. However, its current recommended configuration is 8 GB.

For a new system, 8 GB provides more headroom for plugins, logging, and future expansion.

Does OPNsense Need a High-Performance CPU?

Not for basic routing.

CPU requirements increase significantly when you add VPN, IDS/IPS, traffic inspection, or virtualization.

Does OPNsense Require an Intel NIC?

Not absolutely.

However, the official OPNsense hardware documentation specifically recommends Intel network interfaces because of driver reliability and relatively low CPU overhead.

Choose OPNsense Hardware Around the Workload

A practical selection order is:

Network Speed → Firewall Services → Port Count → CPU → RAM

For most modern home networks, a low-power multi-core CPU, 8 GB of RAM, SSD storage, and multiple 2.5GbE interfaces provide a practical starting point.

If you also need VPN, IDS/IPS, virtualization, or 10GbE networking, leave more hardware headroom.

Related Guide: CWWK Firewall Mini PC Guide

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