Ansible role dhcp

Ansible role for setting up ISC DHCPD. The responsibilities of this role are to install packages and manage the configuration (dhcpd.conf(5)). Managing the firewall configuration is NOT a concern of this role. You can do this in your local playbook, or use another role (e.g. bertvv.rh-base.

Refer to the change log for notable changes in each release.

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Requirements

No specific requirements

Role Variables

This role is able to set global options, and to specify subnet declarations.

See the test playbook for a working example of a DHCP server in a test environment based on Vagrant and VirtualBox. This section is a reference of all supported options.

Global options

The following variables, when set, will be added to the global section of the DHCP configuration file. If there is no default value specified, the corresponding setting will be left out of dhcpd.conf(5).

See the dhcp-options(5) man page for more information about these options.

Remarks

(1) This role supports the definition of classes with a match statement, e.g.:

# Class for VirtualBox VMs
dhcp_global_classes:
  - name: vbox
    match: 'match if binary-to-ascii(16,8,":",substring(hardware, 1, 3)) = "8:0:27"'

Class names can be used in the definition of address pools (see below).

(2) The role variable dhcp_global_domain_name_servers may be written either as a list (when you have more than one item), or as a string (when you have only one). The following snippet shows an example of both:

# A single DNS server
dhcp_global_domain_name_servers: 8.8.8.8

# A list of DNS servers
dhcp_global_domain_name_servers:
  - 8.8.8.8
  - 8.8.4.4

(3) This role also supports the definition of a failover peer, e.g.:

# Failover peer definition
dhcp_global_failover_peer: failover-group
dhcp_global_failover:
  role: primary # | secondary
  address: 192.168.222.2
  port: 647
  peer_address: 192.168.222.3
  peer_port: 647
  max_response_delay: 15
  max_unacked_updates: 10
  load_balance_max_seconds: 5
  split: 255
  mclt: 3600

The variable dhcp_global_failover_peer contains a name for the configured peer, to be used on a per pool basis. The failover declaration options are specified with the variable dhcp_global_failover, a dictionary that may contain the following options:

The failover peer directive has to be in the definition of address pools (see below).

Subnet declarations

The role variable dhcp_subnets contains a list of dicts, specifying the subnet declarations to be added to the DHCP configuration file. Every subnet declaration should have an ip and netmask, other options are not mandatory. We start this section with an example, a complete overview of supported options follows.

dhcp_subnets:
  - ip: 192.168.222.0
    netmask: 255.255.255.128
    domain_name_servers:
      - 10.0.2.3
      - 10.0.2.4
    range_begin: 192.168.222.50
    range_end: 192.168.222.127
  - ip: 192.168.222.128
    default_lease_time: 3600
    max_lease_time: 7200
    netmask: 255.255.255.128
    domain_name_servers: 10.0.2.3
    routers: 192.168.222.129

An alphabetical list of supported options in a subnet declaration:

You can specify address pools within a subnet by setting the pools options. This allows you to specify a pool of addresses that will be treated differently than another pool of addresses, even on the same network segment or subnet. It is a list of dicts with the following keys, all of which are optional:

(1) For the allow and deny fields, the options are enumerated in dhcpd.conf(5), but include:

• booting
• bootp
• client-updates
• known-clients
• members of "CLASS"
• unknown-clients

(2) For multiple subnet ranges, they can be specified, thus:

ranges:
  - { begin: 192.168.222.50, end: 192.168.222.99 }
  - { begin: 192.168.222.110, end: 192.168.222.127 }

Host declarations

You can specify hosts that should get a fixed IP address based on their MAC by setting the dhcp_hosts option. This is a list of dicts with the following three keys, of which name and mac are mandatory:

dhcp_hosts:
  - name: cl1
    mac: '00:11:22:33:44:55'
    ip: 192.168.222.150
  - name: cl2
    mac: '00:de:ad:be:ef:00'
    ip: 192.168.222.151

Specify PXEBoot server

Setting the variable dhcp_pxeboot_server, will redirect PXE clients to the specified PXEBoot server in order to boot over the network. The specified server should have boot images on the expected locations. Use e.g. bertvv.pxeserver to configure it.

Custom Includes

Setting the variable dhcp_custom_inludes to a jinja template will allow custom configurations to be used which will subsequently be included into the dhcpd.conf file. If the template file name has the .j2 extension it will be removed from the destination file name, else it will preserve the template file name in the destination.

dhcp_custom_includes:
  - custom-dhcp-config.conf[.j2]

The default mode for the destination custom config file is 0644. To modify this set the variable dhcp_custom_includes_modes. The zip_longest filter will be used in conjunction with dhcp_custom_includes variable.

dhcp_custom_includes_modes:
  - '0600'

You can create your own variables to use within the template allowing for total flexibility. To avoid variable conflicts make sure that you use variables that are not referenced within this role as this will duplicate configuration in multiple .conf files.

    dhcp_custom_hosts:
      - name: Juniper1
        mac: 'de:ad:c0:de:ca:fe'
        ip: 192.168.35.160
        options:
          - name: tftp-server-name
            value: 192.168.35.152
          - name: host-name
            value: Juniper1
          - name: NEW_OP.transfer-mode
            value: "http"
          - name: NEW_OP.config-file-name
            value: "/configurations/j1-switch.config"

Finally the jinja template must contain valid ISC DHCPD configuration (dhcpd.conf(5)). This is an example of using bertvv.dhcp for juniper Zero-Touch-Provisioning.

option space NEW_OP;
option NEW_OP.image-file-name code 0 = text;
option NEW_OP.config-file-name code 1 = text;
option NEW_OP.image-file-type code 2 = text;
option NEW_OP.transfer-mode code 3 = text;
option NEW_OP.alt-image-file-name code 4= text;
option NEW_OP.http-port code 5= text;
option NEW_OP-encapsulation code 43 = encapsulate NEW_OP;

{% if dhcp_custom_hosts is defined %}

#
# Host declarations
#
{% for host in dhcp_custom_hosts %}
host {{ host.name | replace (" ","_") | replace ("'","_") | replace (":","_") }} {
  hardware ethernet {{ host.mac }};
{% if host.ip is defined %}
  fixed-address {{ host.ip }};
{% endif %}
{% if host.options is defined %}
{% for option in host.options %}
  {{ option.name }} "{{ option.value }}"
{% endfor %}
{% endif %}
}
{% endfor %}
{% endif %}

Dependencies

No dependencies.

Example Playbook

See the test playbook

Testing

To run the tests for this playbook, you need to have Molecule, VirtualBox and Vagrant installed. Running the command molecule converge will create a VirtualBox VM with a host-only interface with IP address 192.168.222.2. To test, you can e.g. use the nmap dhcp-discover script:

$ sudo nmap --script broadcast-dhcp-discover -e vboxnet7
Starting Nmap 7.91 ( https://nmap.org ) at 2021-11-30 11:32 CET
Pre-scan script results:
| broadcast-dhcp-discover: 
|   Response 1 of 2: 
|     Interface: vboxnet7
|     IP Offered: 192.168.222.50
|     DHCP Message Type: DHCPOFFER
|     Server Identifier: 192.168.222.2
|     IP Address Lease Time: 5m00s
|     Subnet Mask: 255.255.255.0
|     Domain Name Server: 10.0.2.3, 10.0.2.4
|     Domain Name: example.com
|     Broadcast Address: 192.168.222.255
|   Response 2 of 2: 
|     Interface: vboxnet7
|     IP Offered: 192.168.222.50
|     DHCP Message Type: DHCPOFFER
|     Server Identifier: 192.168.222.2
|     IP Address Lease Time: 5m00s
|     Subnet Mask: 255.255.255.0
|     Domain Name Server: 10.0.2.3, 10.0.2.4
|     Domain Name: example.com
|_    Broadcast Address: 192.168.222.255
WARNING: No targets were specified, so 0 hosts scanned.
Nmap done: 0 IP addresses (0 hosts up) scanned in 10.19 seconds

License

BSD

Contributing

Issues, feature requests, ideas are appreciated and can be posted in the Issues section. Pull requests are also very welcome. Preferably, create a topic branch and when submitting, squash your commits into one (with a descriptive message).

Contributors

• Ahmed Sghaier
• Alessandro Ogier
• Alex Gittings
• Bert Van Vreckem (maintainer)
• Birgit Croux
• @cacheira
• @donvipre
• Fabio Rocha
• Felix Egli
• Guillaume Parent
• Jan Bundesmann
• Jonathan Piron
• Josh Benner
• Josh Cummings
• @jpiron
• @lijok
• Maxim Baranov
• @RayfordJ
• Rian Bogle
• Stuart Knight (maintainer)
• Valentin Delaye