26zl Configuring pfSense Firewall Rules
When to Use
- Deploying a perimeter or internal firewall to segment and protect network zones (DMZ, internal, guest, IoT)
- Creating granular access control rules to restrict traffic between VLANs and network segments
- Configuring NAT rules for port forwarding to internal services exposed to the internet
- Setting up site-to-site or remote access VPN tunnels using IPsec or OpenVPN
- Implementing traffic shaping and bandwidth management for quality-of-service requirements
Do not use as a substitute for host-based firewalls on individual systems, for SSL/TLS deep packet inspection without dedicated hardware acceleration, or as the sole security control without complementary IDS/IPS.
Prerequisites
- pfSense 2.7+ installed on dedicated hardware or virtual machine with at least two network interfaces
- Access to the pfSense WebConfigurator (default: https://192.168.1.1)
- Network topology diagram showing all interfaces, VLANs, and desired traffic flow
- DNS and DHCP configuration planned for each network zone
- Understanding of TCP/IP, NAT, and stateful firewall concepts
Workflow
Step 1: Configure Network Interfaces and VLANs
Access the pfSense WebConfigurator and define interfaces:
Navigate: Interfaces > Assignments
WAN Interface (igb0):
- Type: DHCP or Static IP from ISP
- Block private networks: Enabled
- Block bogon networks: Enabled
LAN Interface (igb1):
- IPv4: 10.10.1.1/24
- Description: CORPORATE_LAN
Create VLANs:
Navigate: Interfaces > VLANs > Add
- VLAN 10 on igb1: DMZ (10.10.10.1/24)
- VLAN 20 on igb1: SERVERS (10.10.20.1/24)
- VLAN 30 on igb1: GUEST (10.10.30.1/24)
- VLAN 40 on igb1: IOT (10.10.40.1/24)
Assign VLANs:
Navigate: Interfaces > Assignments > Add each VLAN
Enable each interface and assign the gateway IP
Step 2: Configure DHCP and DNS for Each Zone
Navigate: Services > DHCP Server
CORPORATE_LAN (10.10.1.0/24):
Range: 10.10.1.100 - 10.10.1.200
DNS: 10.10.20.10 (internal DNS server)
Gateway: 10.10.1.1
DMZ (10.10.10.0/24):
Range: 10.10.10.100 - 10.10.10.200
DNS: 10.10.20.10
Gateway: 10.10.10.1
GUEST (10.10.30.0/24):
Range: 10.10.30.100 - 10.10.30.200
DNS: 1.1.1.1, 8.8.8.8 (public DNS only)
Gateway: 10.10.30.1
Navigate: Services > DNS Resolver
Enable DNS Resolver on all interfaces except GUEST
Enable DNSSEC
Configure forwarding to upstream DNS servers
Step 3: Create Firewall Rule Aliases
Navigate: Firewall > Aliases
RFC1918_Networks:
Type: Network
Values: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
WebPorts:
Type: Port
Values: 80, 443
ManagementPorts:
Type: Port
Values: 22, 3389, 5900
CriticalServers:
Type: Host
Values: 10.10.20.10, 10.10.20.11, 10.10.20.12
BlockedCountries:
Type: URL Table
URL: https://www.ipdeny.com/ipblocks/data/aggregated/cn-aggregated.zone
Update: 24 hours
Step 4: Implement Firewall Rules by Zone
Navigate: Firewall > Rules
=== WAN Rules ===
# Block all inbound by default (implicit deny)
# Allow established/related traffic (automatic in pfSense stateful mode)
# Allow inbound to DMZ web server (via NAT)
Action: Pass | Interface: WAN | Protocol: TCP
Source: any | Destination: WAN Address | Port: 80, 443
Description: Allow HTTP/HTTPS to DMZ web server
=== LAN Rules ===
# Allow LAN to access internal servers
Action: Pass | Interface: LAN | Protocol: TCP
Source: LAN net | Destination: SERVERS net | Port: WebPorts, 3306, 5432
Description: Allow LAN to internal web and database servers
# Allow LAN to internet
Action: Pass | Interface: LAN | Protocol: any
Source: LAN net | Destination: ! RFC1918_Networks
Description: Allow LAN to internet (block inter-VLAN via RFC1918 exclusion)
# Block LAN to IoT (explicit deny before implicit allow)
Action: Block | Interface: LAN | Protocol: any
Source: LAN net | Destination: IOT net
Description: Block direct LAN to IoT communication
=== DMZ Rules ===
# Allow DMZ web servers to query internal DNS
Action: Pass | Interface: DMZ | Protocol: TCP/UDP
Source: DMZ net | Destination: 10.10.20.10 | Port: 53
Description: Allow DMZ DNS queries to internal resolver
# Allow DMZ to internet for updates only
Action: Pass | Interface: DMZ | Protocol: TCP
Source: DMZ net | Destination: any | Port: 80, 443
Description: Allow DMZ outbound HTTP/HTTPS for updates
# Block all other DMZ traffic
Action: Block | Interface: DMZ | Protocol: any
Source: DMZ net | Destination: any
Description: Default deny for DMZ
=== GUEST Rules ===
# Allow guest to internet only (DNS and web)
Action: Pass | Interface: GUEST | Protocol: TCP/UDP
Source: GUEST net | Destination: ! RFC1918_Networks | Port: 53, 80, 443
Description: Allow guest internet access only
# Block all guest to internal
Action: Block | Interface: GUEST | Protocol: any
Source: GUEST net | Destination: RFC1918_Networks
Description: Block guest access to all internal networks
=== IOT Rules ===
# Allow IoT to specific cloud endpoints
Action: Pass | Interface: IOT | Protocol: TCP
Source: IOT net | Destination: ! RFC1918_Networks | Port: 443, 8883
Description: Allow IoT HTTPS and MQTT to cloud
# Block IoT inter-device communication
Action: Block | Interface: IOT | Protocol: any
Source: IOT net | Destination: IOT net
Description: Prevent IoT lateral movement
# Block IoT to all internal networks
Action: Block | Interface: IOT | Protocol: any
Source: IOT net | Destination: RFC1918_Networks
Description: Block IoT access to internal
Step 5: Configure NAT Rules
Navigate: Firewall > NAT > Port Forward
# Web server in DMZ
Interface: WAN | Protocol: TCP
Destination: WAN address | Port: 443
Redirect target IP: 10.10.10.50 | Port: 443
NAT Reflection: Enable
Description: HTTPS to DMZ web server
# SSH jump host (non-standard port)
Interface: WAN | Protocol: TCP
Destination: WAN address | Port: 2222
Redirect target IP: 10.10.20.11 | Port: 22
Description: SSH to internal jump host via port 2222
Navigate: Firewall > NAT > Outbound
Mode: Hybrid Outbound NAT
# Add rule for DMZ servers to use a dedicated public IP
Interface: WAN | Source: 10.10.10.0/24
Translation Address: <dedicated_public_ip>
Description: DMZ outbound NAT via dedicated IP
Step 6: Enable Logging and Monitoring
Navigate: Status > System Logs > Settings
Remote Logging: Enable
Remote log servers: 10.10.20.15:514 (Syslog/SIEM)
Log firewall default blocks: Enabled
Navigate: Firewall > Rules
Enable logging on critical rules:
- All BLOCK rules
- WAN inbound PASS rules
- Inter-VLAN PASS rules
Navigate: Diagnostics > pfTop
Monitor real-time connection states and bandwidth usage
Install pfBlockerNG package:
Navigate: System > Package Manager > Available Packages
Install pfBlockerNG-devel
Configure IP blocklists (Spamhaus DROP, Emerging Threats)
Configure DNSBL for malware domain blocking
Step 7: Backup and Test Configuration
# Export configuration backup
Navigate: Diagnostics > Backup & Restore
Download XML configuration file
# Test rules from each zone
# From LAN:
curl -I https://10.10.20.10 # Should succeed (LAN to SERVERS)
curl -I https://10.10.40.5 # Should fail (LAN to IOT blocked)
# From GUEST:
curl -I https://www.google.com # Should succeed (internet)
curl -I https://10.10.20.10 # Should fail (guest to internal blocked)
# From DMZ:
nslookup google.com 10.10.20.10 # Should succeed (DNS allowed)
ssh 10.10.1.50 # Should fail (DMZ to LAN blocked)
# Verify logging
Navigate: Status > System Logs > Firewall
Check that blocked and passed traffic is logging correctly
# Schedule automated config backups
Navigate: Diagnostics > AutoConfigBackup
Enable automatic backups to Netgate cloud or local storage
Key Concepts
| Term | Definition |
|---|---|
| Stateful Firewall | Firewall that tracks the state of network connections and automatically allows return traffic for established sessions without explicit rules |
| Alias | Named group of IP addresses, networks, or ports in pfSense that simplifies rule management and improves readability |
| NAT (Network Address Translation) | Translation of IP addresses between internal and external networks, including port forwarding for inbound access to internal services |
| Floating Rules | pfSense rules that apply across multiple interfaces simultaneously, processed before per-interface rules |
| pfBlockerNG | pfSense package that integrates IP reputation blocklists and DNS-based blocklists for automated threat blocking |
| Rule Processing Order | pfSense evaluates rules top-to-bottom within each interface tab; first match wins, and unmatched traffic is blocked by default |
Tools & Systems
- pfSense 2.7+: Open-source firewall and router platform based on FreeBSD with web-based management and extensive package ecosystem
- pfBlockerNG: IP and DNS blocklist package for automated threat intelligence integration
- Snort/Suricata packages: IDS/IPS integration available as pfSense packages for inline traffic inspection
- OpenVPN/IPsec: Built-in VPN implementations for site-to-site and remote access connectivity
- Netgate AutoConfigBackup: Cloud-based configuration backup service for pfSense disaster recovery
Common Scenarios
Scenario: Segmenting a Small Business Network with pfSense
Context: A medical practice needs to segment its network to meet HIPAA requirements. They have a single internet connection, an electronic health records (EHR) server, staff workstations, a guest WiFi network, and medical IoT devices (vitals monitors, imaging equipment). Budget constraints require an open-source solution.
Approach:
- Deploy pfSense on a Netgate 4100 appliance with four physical interfaces (WAN, LAN, DMZ, MGMT)
- Create VLANs for staff (VLAN 10), EHR servers (VLAN 20), guest WiFi (VLAN 30), and medical devices (VLAN 40)
- Configure strict rules: staff VLAN can access EHR servers on HTTPS only; medical devices can communicate only with the EHR server on specific ports; guest WiFi gets internet-only access with no internal routing
- Enable pfBlockerNG with healthcare-specific threat feeds and malware domain blocking
- Configure outbound NAT to prevent internal IP addresses from leaking to the internet
- Enable comprehensive logging and forward all firewall logs to a SIEM via syslog
- Set up automated configuration backups and document the rule base for audit compliance
Pitfalls:
- Creating rules that are too permissive ("allow any any") instead of specific port-based rules
- Forgetting the rule processing order -- placing a broad PASS rule above a specific BLOCK rule
- Not enabling logging on critical rules, making incident investigation impossible
- Allowing IoT devices unrestricted internet access, creating potential data exfiltration paths
Output Format
## pfSense Firewall Configuration Report
**Device**: pfSense 2.7.2 on Netgate 4100
**Interfaces**: WAN (igb0), LAN (igb1), DMZ (igb2), MGMT (igb3)
**VLANs**: 4 configured (Staff, Servers, Guest, IoT)
**Total Rules**: 28 active rules across all interfaces
### Rule Summary by Interface
| Interface | Pass Rules | Block Rules | Logging Enabled |
|-----------|-----------|-------------|-----------------|
| WAN | 2 | 1 (default) | Yes |
| LAN | 4 | 2 | Yes (blocks) |
| DMZ | 3 | 1 (default) | Yes |
| GUEST | 1 | 2 | Yes |
| IOT | 1 | 3 | Yes |
### Security Controls
- pfBlockerNG: 12 IP blocklists + DNSBL enabled
- Snort IDS: Running on WAN and LAN interfaces
- VPN: OpenVPN remote access configured with MFA
- Logging: All traffic forwarded to SIEM (10.10.20.15)