DHCP Server

Multiple DHCP Servers can be run from a single machine. Each DHCP service is identified by a shared-network-name.

DHCP Server Example

In this example, we are offering address space in the 172.16.17.0/24 network, which is on eth1, and pppoe0 is our connection to the internet. We are using the network name dhcpexample.

Prerequisites

Configuring the PPPoE interface is assumed to be done already, and appears on pppoe0

Interface Configuration

set interface ethernet eth1 address 172.16.17.1/24

Multiple ranges can be defined and can contain holes.

set service dhcp-server shared-network-name dhcpexample authoritative
set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 default-router 172.16.17.1
set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 dns-server 172.16.17.1
set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 lease 86400
set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 range 0 start 172.16.17.100
set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 range 0 stop 172.16.17.199

Explanation

  • set service dhcp-server shared-network-name dhcpexample authoritative

    This says that this device is the only DHCP server for this network. If other devices are trying to offer DHCP leases, this machine will send ‘DHCPNAK’ to any device trying to request an IP address that is not valid for this network.

  • set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 default-router 172.16.17.1

    This is a configuration parameter for the subnet, saying that as part of the response, tell the client that I am the default router for this network

  • set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 dns-server 172.16.17.1

    This is a configuration parameter for the subnet, saying that as part of the response, tell the client that I am the DNS server for this network. If you do not want to run a DNS server, you could also provide one of the public DNS servers, such as google’s. You can add multiple entries by repeating the line.

  • set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 lease 86400

    Assign the IP address to this machine for 24 hours. It is unlikely you’d need to shorten this period, unless you are running a network with lots of devices appearing and disappearing.

  • set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 range 0 start 172.16.17.100

    Make a range of addresses available for clients starting from .100 […]

  • set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 range 0 stop 172.16.17.199

    […] and ending at .199

Failover

VyOS provides support for DHCP failover:

set service dhcp-server shared-network-name 'LAN' subnet '192.168.0.0/24' failover local-address '192.168.0.1'
set service dhcp-server shared-network-name 'LAN' subnet '192.168.0.0/24' failover name 'foo'
set service dhcp-server shared-network-name 'LAN' subnet '192.168.0.0/24' failover peer-address '192.168.0.2'

Note

name must be identical on both sides!

The primary and secondary statements determines whether the server is primary or secondary

set service dhcp-server shared-network-name 'LAN' subnet '192.168.0.0/24' failover status 'primary'

or

set service dhcp-server shared-network-name 'LAN' subnet '192.168.0.0/24' failover status 'secondary'

Note

In order for the primary and the secondary DHCP server to keep their lease tables in sync, they must be able to reach each other on TCP port 647. If you have firewall rules in effect, adjust them accordingly.

Static mappings MAC/IP

set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 static-mapping static-mapping-01 ip-address 172.16.17.10
set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 static-mapping static-mapping-01 mac-address ff:ff:ff:ff:ff:ff

DHCP server options

default-router (DHCP option 003)
set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 default-router <ROUTER-IP>
dns-server (DHCP option 006)
set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 dns-server <DNS-SERVER-IP>
domain-name Client domain name (DHCP option 015)
set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 domain-name "<DOMAIN-NAME>"
domain-search (DHCP option 119)
This option can be given multiple times if you need multiple search domains set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 domain-search "<DOMAIN_NAME_1>" set service dhcp-server shared-network-name dhcpexample subnet 172.16.17.0/24 domain-search "<DOMAIN_NAME_2>"

DHCPv6 server

VyOS provides DHCPv6 server functionality which is described in this section. In order to use the DHCPv6 server it has to be enabled first:

set service dhcpv6-server

To restart the DHCPv6 server (operational mode):

restart dhcpv6 server

To show the current status of the DHCPv6 server use:

show dhcpv6 server status

Show statuses of all assigned leases:

show dhcpv6 server leases

DHCPv6 server options

DHCPv6 server preference value

Clients receiving advertise messages from multiple servers choose the server with the highest preference value. The range for this value is 0…255. Set a preference value for the DHCPv6 server:

set service dhcpv6-server preference <preference value>

Delete a preference:

set service dhcpv6-server preference

Show current preference:

show service dhcpv6-server preference

Specify address lease time

The default lease time for DHCPv6 leases is 24 hours. This can be changed by supplying a default-time, maximum-time and minimum-time (all values in seconds):

set service dhcpv6-server shared-network-name <name> subnet <ipv6net> lease-time {default <default-time> | maximum <maximum-time> | minimum <minimum-time>}

Reset the custom lease times:

delete service dhcpv6-server shared-network-name <name> subnet <ipv6net> lease-time {default | maximum | minimum}

Show the current configuration:

show service dhcpv6-server shared-network-name <name> subnet <ipv6net> lease-time {default | maximum | minimum}

Specify NIS domain

A Network Information (NIS) domain can be set to be used for DHCPv6 clients:

set service dhcpv6-server shared-network-name <name> subnet <ipv6net> nis-domain <nis-domain-name>

To Delete the NIS domain:

delete service dhcpv6-server shared-network-name <name> subnet <ipv6net> nis-domain <nis-domain-name>

Show a configured NIS domain:

show service dhcpv6-server shared-network-name <name> subnet <ipv6net> nis-domain <nis-domain-name>

Specify NIS+ domain

The procedure to specify a Network Information Service Plus (NIS+) domain is similar to the NIS domain one:

set service dhcpv6-server shared-network-name <name> subnet <ipv6net> nisplus-domain <nisplus-domain-name>

To Delete the NIS+ domain:

delete service dhcpv6-server shared-network-name <name> subnet <ipv6net> nisplus-domain <nisplus-domain-name>

Show a configured NIS domain:

# show service dhcpv6-server shared-network-name <name> subnet <ipv6net> nisplus-domain <nisplus-domain-name>

Specify NIS server address

To specify a NIS server address for DHCPv6 clients:

set service dhcpv6-server shared-network-name <name> subnet <ipv6net> nis-server <IPv6 address>

Delete a specified NIS server address:

delete service dhcpv6-server shared-network-name <name> subnet <ipv6net> nis-server <IPv6 address>

Show specified NIS server addresses:

show service dhcpv6-server shared-network-name <name> subnet <ipv6net> nis-server

Specify NIS+ server address

To specify a NIS+ server address for DHCPv6 clients:

set service dhcpv6-server shared-network-name <name> subnet <ipv6net> nisplus-server <IPv6 address>

Delete a specified NIS+ server address:

delete service dhcpv6-server shared-network-name <name> subnet <ipv6net> nisplus-server <IPv6 address>

Show specified NIS+ server addresses:

show service dhcpv6-server shared-network-name <name> subnet <ipv6net> nisplus-server

Specify a SIP server address for DHCPv6 clients

By IPv6 address

A Session Initiation Protocol (SIP) server address can be specified for DHCPv6 clients:

set service dhcpv6-server shared-network-name <name> subnet <ipv6net> sip-server-address <IPv6 address>

Delete a specified SIP server address:

delete service dhcpv6-server shared-network-name <name> subnet <ipv6net> sip-server-address <IPv6 address>

Show specified SIP server addresses:

show service dhcpv6-server shared-network-name <name> subnet <ipv6net> sip-server-address

By FQDN

A name for SIP server can be specified:

set service dhcpv6-server shared-network-name <name> subnet <ipv6net> sip-server-name <sip-server-name>

Delete a specified SIP server name:

delete service dhcpv6-server shared-network-name <name> subnet <ipv6net> sip-server-name <sip-server-name>

Show specified SIP server names:

show service dhcpv6-server shared-network-name <name> subnet <ipv6net> sip-server-name

Simple Network Time Protocol (SNTP) server address for DHCPv6 clients

A SNTP server address can be specified for DHCPv6 clients:

set service dhcpv6-server shared-network-name <name> subnet <ipv6net> sntp-server-address <IPv6 address>

Delete a specified SNTP server address:

delete service dhcpv6-server shared-network-name <name> subnet <ipv6net> sntp-server-address <IPv6 address>

Show specified SNTP server addresses:

show service dhcpv6-server shared-network-name <name> subnet <ipv6net> sntp-server-address

DHCPv6 address pools

DHCPv6 address pools must be configured for the system to act as a DHCPv6 server. The following example describes a common scenario.

Example 1: DHCPv6 address pool

A shared network named NET1 serves subnet 2001:db8:100::/64 which is connected to eth1, a DNS server at 2001:db8:111::111 is used for name services. The range of the address pool shall be ::100 through ::199. The lease time will be left at the default value which is 24 hours.

set service dhcpv6-server shared-network-name NET1 subnet 2001:db8:100::/64 address-range start 2001:db8:100::100 stop 2001:db8:100::199
set service dhcpv6-server shared-network-name NET1 subnet 2001:db8:100::/64 name-server 2001:db8:111::111

Commit the changes and show the configuration:

commit
show service dhcpv6-server
    shared-network-name NET1 {
        subnet 2001:db8:100::/64 {
           address-range {
              start 2001:db8:100::100 {
                 stop 2001:db8:100::199
              }
           }
           name-server 2001:db8:111::111
        }
    }

Static mappings

In order to map specific IPv6 addresses to specific hosts static mappings can be created. The following example explains the process.

Example 1: Static IPv6 MAC-based mapping

IPv6 address 2001:db8:100::101 shall be statically mapped to a device with MAC address 00:15:c5:b7:5e:23, this host-specific mapping shall be named client1.

Note

The MAC address identifier is defined by the last 4 byte of the MAC address.

set service dhcpv6-server shared-network-name NET1 subnet 2001:db8:100::/64 static-mapping client1 ipv6-address 2001:db8:100::101
set service dhcpv6-server shared-network-name NET1 subnet 2001:db8:100::/64 static-mapping client1 identifier c5b75e23

Commit the changes and show the configuration:

show service dhcp-server shared-network-name NET1
   shared-network-name NET1 {
       subnet 2001:db8:100::/64 {
          name-server 2001:db8:111::111
          address-range {
              start 2001:db8:100::100 {
                 stop 2001:db8:100::199 {
              }
          }
          static-mapping client1 {
             ipv6-address 2001:db8:100::101
             identifier c5b75e23
          }
       }
    }