Basic Firewall Configuration Example

This article is designed to describe how pfSense® software performs rule matching and a basic strict set of rules. The approach described in this document is not the most secure, but will help show how rules are setup.

Rules on the Interface tabs are matched on the incoming interface.

See also

Read the Using Aliases to Simplify Firewall Rules article as it will make management of rules easier.

Basic lock down of the LAN and DMZ outgoing rules

Outbound LAN

Make sure the Default LAN > any rule is either disabled or removed.

  1. Allowing DNS access:

    • If pfSense is the DNS server:

      • Allow TCP/UDP 53 (DNS) from LAN subnet to LAN Address.

    • If using Upstream DNS Servers:

      • Allow TCP/UDP 53 (DNS) from LAN subnet to Upstream DNS Servers.

    • Otherwise:

      • Allow TCP/UDP 53 (DNS) from LAN subnet to anywhere.

  2. Allowing all users to browse web pages anywhere:

    • Allow TCP 80 (HTTP) from LAN subnet to anywhere.

  3. Allowing users to browse secure web pages anywhere:

    • Allow TCP 443 (HTTPS) from LAN subnet to anywhere.

  4. Allowing users to access FTP sites anywhere:

    • Allow TCP 21 (FTP) from LAN subnet to anywhere.

  5. Allowing users to access SMTP on a mail server somewhere:

    • Allow TCP 25 (SMTP) from LAN subnet to anywhere.

  6. Allowing users to access POP3 on a mail server somewhere:

    • Allow TCP 110 (POP3) from LAN subnet to anywhere.

  7. Allowing users to access IMAP on a mail server somewhere:

    • Allow TCP 143 (IMAP) from LAN subnet to anywhere.

  8. Allowing remote connections to an outside windows server for remote administration:

    • Allow TCP/UDP 3389 (Terminal server) from LAN subnet to IP address of remote server.

  9. Allowing LAN to access windows shares on the DMZ, via NETBIOS/Microsoft-DS:

    • Allow TCP/UDP 137 from LAN subnet (NETBIOS) to DMZ subnet.

    • Allow TCP/UDP 138 from LAN subnet (NETBIOS) to DMZ subnet.

    • Allow TCP/UDP 139 from LAN subnet (NETBIOS) to DMZ subnet.

    • Allow TCP 445 from LAN subnet (NETBIOS) to DMZ subnet.

Outbound DMZ

By default, there are no rules on OPT interfaces.

  1. Allowing servers to use Windows update or browse the WAN:

    • Allow TCP 80 from DMZ subnet (HTTP) to anywhere.

    • Allow TCP 443 from DMZ subnet (HTTP) to anywhere.

  2. Allow users to connect to an external DNS server:

    • Allow TCP/UDP 53 from DMZ subnet (DNS) to IP address of the upstream DNS server(s)

  3. Allowing servers to use a remote time server:

    • If using an upstream remote time server:

      • Allow UDP 123 from DMZ subnet (NTP) to IP address of remote time server.

    • Otherwise:

      • Allow UDP 123 from DMZ subnet (NTP) to any.

Setup isolating LAN and DMZ, each with unrestricted Internet access

The following setup can be used instead if outbound access is more lenient, but still controlled between local interfaces. This assumes all local networks are privately numbered, and that interfaces have already been configured.

Create an alias, Firewall > Aliases from the main menu, called RFC1918 containing 192.168.0.0/16, 172.16.0.0/12, and 10.0.0.0/8.

LAN Configuration

  1. For DNS from the firewall:

    • Allow TCP/UDP from LAN subnet to LAN Address port 53.

  2. For accessing the GUI:

    • Allow TCP from LAN subnet to LAN address port 443.

  3. To ping the firewall from the LAN:

    • Allow ICMP from LAN subnet to LAN address.

  4. If there is any traffic required from LAN to DMZ:

    • Allow any traffic required from LAN to DMZ.

  5. Do not allow LAN to reach DMZ or other private networks:

    • Reject Any from LAN subnet to RFC1918.

  6. For internet access:

    • Allow Any from LAN subnet to any.

DMZ Configuration

  1. For DNS from the firewall:

    • Allow TCP/UDP from DMZ subnet to DMZ Address port 53.

  2. For accessing the GUI (optional):

    • Allow TCP from DMZ subnet to DMZ address port 443.

  3. To ping the firewall from the DMZ:

    • Allow ICMP from DMZ subnet to DMZ address.

  4. If there is any traffic required from DMZ to LAN:

    • Allow any traffic required from DMZ to LAN.

  5. Do not allow DMZ to reach LAN or other private networks:

    • Reject Any from DMZ subnet to RFC1918.

  6. For Internet access:

    • Allow Any from DMZ subnet to any.

Additional Interfaces

Repeat the above pattern as needed.