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ansible/roles/dhcp/README.md
Salt a326f5d35d Here have a DHCP server
2021-02-27 08:42:15 -06:00

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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.

Do you use/like this role? Please consider giving it a star. If you rate this role on Ansible Galaxy and find it lacking in some respect, please consider opening an Issue with actionable feedback or a PR so we can improve it. Thank you!

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.

Variable Comments
dhcp_global_authoritative Global authoritative statement (authoritative, not authoritative)
dhcp_global_booting Global booting (allow, deny, ignore)
dhcp_global_bootp Global bootp (allow, deny, ignore)
dhcp_global_broadcast_address Global broadcast address
dhcp_global_classes Class definitions with a match statement(1)
dhcp_global_default_lease_time Default lease time in seconds
dhcp_global_domain_name_servers A list of IP addresses of DNS servers(2)
dhcp_global_domain_name The domain name the client should use when resolving host names
dhcp_global_domain_search A list of domain names to be used by the client to locate non-FQDNs(1)
dhcp_global_failover Failover peer settings (3)
dhcp_global_failover_peer Name for the failover peer (e.g. foo)
dhcp_global_filename Filename to request for boot
dhcp_global_includes_missing Boolean. Continue if includes file(s) missing from role's files/
dhcp_global_includes List of config files to be included (from dhcp_config_dir)
dhcp_global_log_facility Global log facility (e.g. daemon, syslog, user, ...)
dhcp_global_max_lease_time Maximum lease time in seconds
dhcp_global_next_server IP for PXEboot server
dhcp_global_ntp_servers List of IP addresses of NTP servers
dhcp_global_omapi_port OMAPI port
dhcp_global_omapi_secret OMAPI secret
dhcp_global_other_options Array of arbitrary additional global options
dhcp_global_routers IP address of the router
dhcp_global_server_name Server name sent to the client
dhcp_global_server_state Service state (started, stopped)
dhcp_global_subnet_mask Global subnet mask
dhcp_custom_includes List of jinja config files to be included (from dhcp_config_dir)

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:

Option Required Comment
address no This server's IP address
hba no colon-separated-hex-list
load_balance_max_seconds no Cutoff after which load balance is disabled (3 to 5 recommended)
max-balance no Failover pool balance statement
max-lease-misbalance no Failover pool balance statement
max-lease-ownership no Failover pool balance statement
max_response_delay no Maximum seconds without contact before engaging failover
max_unacked_updates no Maximum BNDUPD it can send before receiving a BNDACK (10 recommended)
mclt no Maximum Client Lead Time
min-balance no Failover pool balance statement
peer_address no Failover peer's IP addres
peer_port no This server's port (generally 519/520 or 647/847)
port no This server's port (generally 519/520 or 647/847)
role no primary, secondary
split no Load balance split (0-255)

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:

Option Required Comment
booting no allow,deny,ignore
bootp no allow,deny,ignore
default_lease_time no Default lease time for this subnet (in seconds)
domain_name_servers no List of domain name servers for this subnet(1)
domain_search no List of domain names for resolution of non-FQDNs(1)
filename no filename to retrieve from boot server
hosts no List of fixed IP address hosts for each subnet, similar to dhcp_hosts
ip yes Required. IP address of the subnet
max_lease_time no Maximum lease time for this subnet (in seconds)
netmask yes Required. Network mask of the subnet (in dotted decimal notation)
next_server no IP address of the boot server
ntp_servers no List of NTP servers for this subnet
range_begin no Lowest address in the range of dynamic IP addresses to be assigned
range_end no Highest address in the range of dynamic IP addresses to be assigned
ranges no If multiple ranges are needed, they can be specified as a list (2)
routers no IP address of the gateway for this subnet
server_name no Server name sent to the client
subnet_mask no Overrides the netmask of the 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:

Option Comment
allow Specifies which hosts are allowed in this pool(1)
default_lease_time The default lease time for this pool
deny Specifies which hosts are not allowed in this pool
domain_name_servers The domain name servers to be used for this pool(1)
max_lease_time The maximum lease time for this pool
min_lease_time The minimum lease time for this pool
range_begin The lowest address in this pool
range_end The highest address in this pool
ranges If multiple ranges are needed, they can be specified as a list (2)

(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:

Option Comment
name The name of the host
mac The MAC address of the host
ip The IP address to be assigned to the host 
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]

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

Tests for this role are provided in the form of a Vagrant environment that is kept in a separate branch, vagrant-tests. For more information about setting up the test environment and running the tests, refer to the README of the test branch.

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