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150 lines
5.8 KiB
ReStructuredText
150 lines
5.8 KiB
ReStructuredText
.. _dhcp:
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########
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DHCP(v6)
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########
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VyOS uses ISC DHCPd for both IPv4 and IPv6 address assignment.
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DHCP Server
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===========
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Multiple DHCP Servers can be run from a single machine. Each DHCP service is
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identified by a ``shared-network-name``.
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Basic Example
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-------------
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We are offering address space in the 172.16.17.0/24 network, which is
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physically connected on eth1, and pppoe0 is our connection to the internet.
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We are using the network name `dhcpexample`.
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Prerequisites:
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* Configuring PPPoE interface is assumed to be done already, and appears
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on `pppoe0`
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* Interface ``eth1`` is configured to be connected to our DHCP subnet
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172.16.17.0/24 by assigning e.g. address 172.16.17.1/24.
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Multiple DHCP ranges can be defined and may contain holes.
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.. code-block:: sh
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set service dhcp-server shared-network-name dhcpexample authoritative
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set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 default-router 172.16.17.1
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set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 dns-server 172.16.17.1
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set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 lease 86400
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set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 range 0 start 172.16.17.100
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set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 range 0 stop 172.16.17.199
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Explanation
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^^^^^^^^^^^
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.. cfgcmd:: set service dhcp-server shared-network-name dhcpexample authoritative
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This says that this device is the only DHCP server for this network. If other
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devices are trying to offer DHCP leases, this machine will send 'DHCPNAK' to
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any device trying to request an IP address that is
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not valid for this network.
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.. cfgcmd:: set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 default-router 172.16.17.1
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This is a configuration parameter for the subnet, saying that as part of the
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response, tell the client that I am the default router for this network
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.. cfgcmd:: set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 dns-server 172.16.17.1
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This is a configuration parameter for the subnet, saying that as part of the
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response, tell the client that I am the DNS server for this network. If you
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do not want to run a DNS server, you could also provide one of the public
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DNS servers, such as google's. You can add multiple entries by repeating the
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line.
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.. cfgcmd:: set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 lease 86400
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Assign the IP address to this machine for 24 hours. It is unlikely you'd need
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to shorten this period, unless you are running a network with lots of devices
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appearing and disappearing.
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.. cfgcmd:: set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 range 0 start 172.16.17.100
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Make a range of addresses available for clients starting from .100 [...]
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.. cfgcmd:: set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 range 0 stop 172.16.17.199
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[...] and ending at .199
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Failover
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--------
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VyOS provides support for DHCP failover:
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.. code-block:: sh
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set service dhcp-server shared-network-name 'LAN' subnet '192.168.0.0/24' failover local-address '192.168.0.1'
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set service dhcp-server shared-network-name 'LAN' subnet '192.168.0.0/24' failover name 'foo'
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set service dhcp-server shared-network-name 'LAN' subnet '192.168.0.0/24' failover peer-address '192.168.0.2'
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.. note:: `name` must be identical on both sides!
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The primary and secondary statements determines whether the server is
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primary or secondary
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.. code-block:: sh
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set service dhcp-server shared-network-name 'LAN' subnet '192.168.0.0/24' failover status 'primary'
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or
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.. code-block:: sh
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set service dhcp-server shared-network-name 'LAN' subnet '192.168.0.0/24' failover status 'secondary'
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.. note:: In order for the primary and the secondary DHCP server to keep
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their lease tables in sync, they must be able to reach each other on TCP
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port 647. If you have firewall rules in effect, adjust them accordingly.
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Static mappings
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---------------
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You can specify a static DHCP assignment on a per host basis. You will need the
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MAC address of the station and your desired IP address. The address must be
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inside your subnet definition but can be outside of your range sttement.
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.. cfgcmd:: set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 static-mapping <host> ip-address 172.16.17.10
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Configure desired IPv4 address for your host referenced to as `host`.
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.. cfgcmd:: set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 static-mapping <hodt> mac-address ff:ff:ff:ff:ff:ff
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Configure MAC address for your host referenced by as `host` used in this static
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assignment.
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DHCP Options
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------------
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.. cfgcmd:: set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 default-router '<address>'
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Specify the default routers IPv4 address which should be used in this subnet.
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This can - of course - be a VRRP address (DHCP option 003).
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.. cfgcmd:: set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 dns-server '<address>'
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Specify the DNS nameservers used (Option 006). This option may be used mulltiple
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times to specify additional DNS nameservers.
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.. cfgcmd:: set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 domain-name '<domain-name>'
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The domain-name parameter should be the domain name that will be appended to
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the client's hostname to form a fully-qualified domain-name (FQDN) (DHCP
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Option 015).
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.. cfgcmd:: set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 domain-search '<domain-name>'
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The domain-name parameter should be the domain name used when completing DNS
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request where no full FQDN is passed. This option can be given multiple times
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if you need multiple search domains (DHCP Option 119).
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