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ReStructuredText
207 lines
6.4 KiB
ReStructuredText
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============================
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Transparent Filtering Bridge
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============================
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-------
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Warning
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-------
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The Transparent Filtering Bridge is not compatible with Traffic Shaping.
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Do not enable the traffic shaper when using the filtering bridge.
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--------
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Abstract
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--------
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A transparent firewall can be used to filter traffic without creating
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different subnets. This application is called filtering bridge as it
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acts as a bridge connection two interfaces and applies filtering rules
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on top of this.
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For more information on Filtering Bridged on FreeBSD, see
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`filtering-bridges <https://www.freebsd.org/doc/en/articles/filtering-bridges/article.html>`__
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------------
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Requirements
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------------
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- For this howto we need a basic installation of OPNsense with factory
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defaults as a starting point.
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- And an appliance with 2 physical interfaces.
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--------------
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Considerations
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--------------
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To create this howto version OPNsense 15.7.11 has been used. Some screenshots
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maybe outdated, but setting should apply up to at least 17.1.6. If you use a
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different version some options can be different.
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.. Note::
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The Menu System of the User Interface has been updated with sub items.
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Where tabs are shown in screenshots, these are now likely visible as submenu.
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------------------------------
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Configuration in 10 easy steps
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------------------------------
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.. contents::
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:local:
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.. Warning::
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During the configuration you will be asked to "Apply" your changes several times,
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however this may affect the current connection. So **don't** apply anything until
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completely finished! You need to Save your changes for each step.
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1. Disable Outbound NAT rule generation
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---------------------------------------
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To disable outbound NAT, go to
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:menuselection:`Firewall --> NAT --> Outbound` and select “Disable Outbound NAT rule generation”.
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|Filtering Bridge Step 1.png|
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2. Change system tuneables
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--------------------------
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Enable filtering bridge by changing **net.link.bridge.pfil\_bridge**
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from default to 1 in :menuselection:`System --> Settings --> System Tuneables`.
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|Filtering Bridge Step 2.png|
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And disable filtering on member interfaces by changing
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**net.link.bridge.pfil\_member** from default to 0 in
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:menuselection:`System --> Settings --> System Tuneables`.
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|Filtering Bridge Step2a.png|
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3. Create the bridge
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--------------------
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Create a bridge of LAN and WAN, go to
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:menuselection:`Interfaces --> Other Types --> Bridge`. Add Select LAN and WAN.
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|Filtering Bridge Step 3a.png|
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|Filtering Bridge Step 3b.png|
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4. Assign a management IP/Interface
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-----------------------------------
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To be able to configure and manage the filtering bridge (OPNsense)
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afterwards, we will need to assign a new interface to the bridge and
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setup an IP address.
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Go to :menuselection:`Interfaces --> Assign --> Available network port`, select
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the bridge from the list and hit **+**.
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|Filtering Bridge Step 4.png|
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Now Add an IP address to the interface that you would like to use to
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manage the bridge. Go to :menuselection:`Interfaces --> [OPT1]`, enable the interface
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and fill-in the ip/netmask.
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5. Disable Block private networks & bogon
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-----------------------------------------
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For the WAN interface we nee to disable blocking of private networks & bogus IPs.
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Go to :menuselection:`Interfaces --> [WAN]` and unselect **Block private networks**
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and **Block bogon networks**.
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|Filtering Bridge Step 5.png|
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6. Disable the DHCP server on LAN
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---------------------------------
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To disable the DHCP server on LAN go to :menuselection:`Services --> DHCPv4 --> [LAN]` and
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unselect enable.
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|Filtering Bridge Step 6.png|
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7. Add Allow rules
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-------------------
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After configuring the bridge the rules on member interfaces (WAN/LAN) will be
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ignored. So you can skip this step.
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Add the allow rules for all traffic on each of the three interfaces (WAN/LAN/OPT1).
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This step is to ensure we have a full transparent bridge without any filtering
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taking place. You can setup the correct rules when you have confirmed the bridge
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to work properly.
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Go to :menuselection:`Firewall --> Rules` and add a rule per interface to allow all traffic
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of any type.
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|Filtering Bridge Step 7.png|
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8. Disable Default Anti Lockout Rule
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------------------------------------
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After configuring the bridge the rules on member interfaces (WAN/LAN) will be
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ignored. So you can skip this step.
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As we now have setup allow rules for each interface we can safely remove
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the Anti Lockout rule on LAN
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Go to :menuselection:`Firewall --> Settings --> Admin Access`: Anti-lockout and select
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this option to disable
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9. Set LAN and WAN interface type to 'none'
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-------------------------------------------
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Now remove the IP subnets in use for LAN and WAN by changing the
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interface type to none. Go to :menuselection:`Interfaces --> [LAN]` and :menuselection:`Interfaces --> [WAN]`
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to do so.
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|Filtering Bridge Step 9.png|
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10. Now apply the changes
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-------------------------
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If you followed each step, then you can now apply the changes. The
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Firewall is now converted to a filtering bridge.
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.. rubric:: Done.. ready to set your own filtering rules
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:name: done..-ready-to-set-your-own-filtering-rules
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Now you can create the correct firewall/filter rules and apply them. To
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acces the firewall you need to use the IP adress you configured for the
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OPT1 Interface.
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.. WARNING::
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Rules need to be configured on the bridge. Rules on member interfaces will
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be ignored!
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.. TIP::
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Don't forget to make sure your PC/Laptop is configured with an IP adress that
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falls within the IP range of the OPT1 subnet!
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.. |Filtering Bridge Step 1.png| image:: images/Filtering_Bridge_Step_1.png
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:width: 700px
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.. |Filtering Bridge Step 2.png| image:: images/Filtering_Bridge_Step_2.png
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:class: thumbimage
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:width: 700px
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.. |Filtering Bridge Step2a.png| image:: images/Filtering_Bridge_Step_2a.png
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:class: thumbimage
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:width: 700px
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.. |Filtering Bridge Step 3a.png| image:: images/Filtering_Bridge_Step_3a.png
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:width: 700px
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.. |Filtering Bridge Step 3b.png| image:: images/Filtering_Bridge_Step_3b.png
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:width: 700px
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.. |Filtering Bridge Step 4.png| image:: images/Filtering_Bridge_Step_4.png
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:width: 700px
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.. |Filtering Bridge Step 5.png| image:: images/Filtering_Bridge_Step_5.png
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:width: 700px
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.. |Filtering Bridge Step 6.png| image:: images/Filtering_Bridge_Step_6.png
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:width: 619px
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.. |Filtering Bridge Step 7.png| image:: images/Filtering_Bridge_Step_7.png
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:width: 700px
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:height: 69px
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.. |Filtering Bridge Step 9.png| image:: images/Filtering_Bridge_Step_9.png
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:width: 700px
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