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166 lines
4.0 KiB
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166 lines
4.0 KiB
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DHCP Relay
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----------
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If you want your router to forward DHCP requests to an external DHCP server
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you can configure the system to act as a DHCP relay agent. The DHCP relay
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agent works with IPv4 and IPv6 addresses.
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All interfaces used for the DHCP relay must be configured. See
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https://wiki.vyos.net/wiki/Network_address_setup.
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DHCP relay example
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^^^^^^^^^^^^^^^^^^
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.. figure:: /_static/images/service_dhcp-relay01.png
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:scale: 80 %
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:alt: DHCP relay example
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DHCP relay example
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In this example the interfaces used for the DHCP relay are eth1 and eth2. The
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router receives DHCP client requests on eth1 and relays them through eth2 to
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the DHCP server at 10.0.1.4.
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Configuration
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^^^^^^^^^^^^^
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Enable DHCP relay for eth1 and eth2:
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.. code-block:: sh
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set service dhcp-relay interface eth1
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set service dhcp-relay interface eth2
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Set the IP address of the DHCP server:
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.. code-block:: sh
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set service dhcp-relay server 10.0.1.4
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The router should discard DHCP packages already containing relay agent
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information to ensure that only requests from DHCP clients are forwarded:
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.. code-block:: sh
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set service dhcp-relay relay-options relay-agents-packets discard
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Commit the changes and show the results:
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.. code-block:: sh
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commit
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show service dhcp-relay
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interface eth1
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interface eth2
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server 10.0.1.4
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relay-options {
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relay-agents-packets discard
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}
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The DHCP relay agent can be restarted with:
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.. code-block:: sh
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restart dhcp relay-agent
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DHCPv6 relay example
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^^^^^^^^^^^^^^^^^^^^
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.. figure:: /_static/images/service_dhcpv6-relay01.png
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:scale: 80 %
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:alt: DHCPv6 relay example
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DHCPv6 relay example
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In this example DHCPv6 requests are received by the router on eth1
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(`listening interface`) and forwarded through eth2 (`upstream interface`) to
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the external DHCPv6 server at 2001:db8:100::4.
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Configuration
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*************
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Set eth1 to be the listening interface for the DHCPv6 relay:
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.. code-block:: sh
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set service dhcpv6-relay listen-interface eth1
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Set eth2 to be the upstream interface and specify the IPv6 address of
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the DHCPv6 server:
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.. code-block:: sh
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set service dhcpv6-relay upstream-interface eth2 address 2001:db8:100::4
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Commit the changes and show results:
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.. code-block:: sh
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commit
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show service dhcpv6-relay
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listen-interface eth1 {
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}
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upstream-interface eth2 {
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address 2001:db8:100::4
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}
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Show the current status of the DHCPv6 relay agent:
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.. code-block:: sh
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show dhcpv6 relay-agent status
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The DHCPv6 relay agent can be restarted with:
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.. code-block:: sh
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restart dhcpv6 relay-agent
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Additional parameters
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^^^^^^^^^^^^^^^^^^^^^
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DHCP relay agent options
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************************
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Set the maximum hop count before packets are discarded. Range 0...255,
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default 10.
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* :code:`set service dhcp-relay relay-options hop-count 'count'`
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Set maximum size of DHCP packets including relay agent information. If a
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DHCP packet size surpasses this value it will be forwarded without appending
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relay agent information. Range 64...1400, default 576.
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* :code:`set service dhcp-relay relay-options max-size 'size'`
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Four policies for reforwarding DHCP packets exist:
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* **append:** The relay agent is allowed to append its own relay information
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to a received DHCP packet, disregarding relay information already present in
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the packet.
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* **discard:** Received packets which already contain relay information will
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be discarded.
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* **forward:** All packets are forwarded, relay information already present
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will be ignored.
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* **replace:** Relay information already present in a packet is stripped and
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replaced with the router's own relay information set.
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* :code:`set service dhcp-relay relay-options relay-agents-packet 'policy'`
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DHCPv6 relay agent options
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**************************
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Set maximum hop count before packets are discarded. Default: 10.
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* :code:`set service dhcpv6-relay max-hop-count 'count'`
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If this is set the relay agent will insert the interface ID. This option is
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set automatically if more than one listening interfaces are in use.
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* :code:`set service dhcpv6-relay use-interface-id-option`
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