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5.4 KiB
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====
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DHCP
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====
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DHCP is used to automatically provide clients with an IP address (instead of clients having to set one themselves).
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DHCP is available for both IPv4 and IPv6 clients, referred to as DHCPv4 and DHCPv6, respectively.
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-----------------
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Settings overview
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-----------------
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DHCPv4 settings can be found at :menuselection:`Services --> DHCPv4`. DHCPv6 settings can be found at :menuselection:`Services --> DHCPv6`.
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The DHCPv4 submenu further consists of:
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* An entry per interface of general settings, like a toggle to enable/disable DHCPv4 for this interface, DHCP range, DNS servers…
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* **Relay**: DHCP requests can be “forwarded” to a DHCP server on another interface. This is called relaying.
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* **Leases**: Shows all IP addresses that are handed out to clients (can be filtered to only show active and static leases).
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* **Log File**: Shows the log file of the DHCPv4 server.
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The DHCPv6 submenu further consists of:
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* **Relay**: DHCP requests can be “forwarded” to a DHCP server on another interface. This is called relaying.
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* **Leases**: Shows all IP addresses that are handed out to clients (can be filtered to only show active and static leases).
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------------
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Using DHCPv4
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------------
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A typical DHCPv4 usage scenario is using it on your LAN with an IP range of 192.168.1.x, where x can be a number from 1
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through 254. This means a subnet mask of 255.255.255.0. The range can also be written as 192.168.1.0/24. (The “1” in
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the third group can also be another number, and there are also other ranges available for private use. These are
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described in `RFC 1918 <https://tools.ietf.org/html/rfc1918#section-3>`_.)
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The LAN IP of the OPNsense device that serves DHCP to the LAN should fall in the same DHCP IP range. Typically, it gets
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the address ending in .1 (so 192.168.1.1 in this example).
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To set the LAN IP, go to :menuselection:`Interfaces --> [LAN]`, set “IPv4 Configuration Type” to “Static”, and under
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“Static IPv4 configuration”, set “IPv4 address” to ``192.168.1.1`` and the subnet dropdown to “24”. Then click Save.
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To set the DHCP settings, go to :menuselection:`Services --> DHCPv4 --> [LAN]`. Under “Gateway”, put ``192.168.1.1``. Under range,
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put ``192.168.1.100`` as the start address and ``192.168.1.200`` as the end address. Then click Save. After saving,
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click the “Apply Settings” button.
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------------
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Using DHCPv6
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------------
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.. _Using DHCPv6:
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When IPv6 addresses should be provisioned over DHCPv6 the :menuselection:`Services-->DHCPv6-->[Interface]` is the place
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to look at. Like in the IPv4 scenario, you can provide a range here, offer settings like default DNS servers and
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create static assignments based on the clients unique DHCP identifier (`DUID <https://en.wikipedia.org/wiki/DHCPv6>`__).
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Always make sure :doc:`Router advertisements </manual/radvd>` are properly configured before debugging DHCPv6 issues, these two
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daemons depend on eachother.
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-------------------------
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Advanced settings
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-------------------------
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To configure options that are not available in the GUI one can add custom configuration files on the firewall itself.
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Files can be added in :code:`/usr/local/etc/dhcpd.opnsense.d/` for IPv4 and :code:`/usr/local/etc/dhcpd6.opnsense.d/`
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for IPv6, these should use as extension .conf (e.g. custom-options.conf). When more files are placed inside the directory,
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all will be included in alphabetical order.
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.. Warning::
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It is the sole responsibility of the administrator which places a file in the extension directory to ensure that the configuration is
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valid.
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.. _dhcp-relaying:
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-------------
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DHCP relaying
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-------------
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DHCP relaying is the forwarding of DHCP requests received on one interface to the DHCP server on another. DHCP
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relaying is available for both DHCPv4 and DHCPv6. The DHCPv4 settings can be found at
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:menuselection:`Services --> DHCPv4 --> Relay`. The DHCPv6 settings can be found at
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:menuselection:`Services --> DHCPv6 --> Relay`.
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When setting up DHCP relaying (both DHCPv4 and DHCPv6 relaying have the same settings), the following options are
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available:
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+-----------------------+----------------------------------------------------------------------------------------------+
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| Setting | Explanation |
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+=======================+==============================================================================================+
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| Enable | |
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+-----------------------+----------------------------------------------------------------------------------------------+
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| Interface(s) | Which interfaces to apply relaying to. Only interfaces with an IP can be selected. |
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+-----------------------+----------------------------------------------------------------------------------------------+
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| Append circuit ID and | If this is checked, the DHCP relay will append the circuit ID (interface number) and the |
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| agent ID to requests | agent ID to the DHCP request. |
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+-----------------------+----------------------------------------------------------------------------------------------+
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| Destination servers | A comma separated list of IPs to which the requests should be forwarded. |
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+-----------------------+----------------------------------------------------------------------------------------------+
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