Simple IP Dispenser (SID) is a web service that monitors dnsmasq activity and allows you to easily assign a consistent IP address to a particular device that requests an address from dnsmasq.
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Simple IP Dispenser (SID)

SID is a web service that manages static IP reservations in a dnsmasq configuration file. It monitors requests for IPs and stores the requests in the service. A REST API is provided to allow or deny the requests. If a request is accepted, the MAC of the requester is assigned the next available IP and given a host name (supplied by user or guest#). The service then restarts dnsmasq at which point the requester should be given an IP address by dnsmasq.

While potentially being able to be used anywhere, this service was designed to run on a Raspberry Pi configured to be a DNS/DHCP server. Specifically, this service compliments my article describing dnsmasq configuration on a Raspberry Pi.


This service installs on a Raspberry Pi using a Debian package. First, make sure you have the dependencies installed in order to build a Debian package:

sudo apt-get install build-essentials debhelper devscripts

Then, to build the package, clone the repo, then run:

cd sid/src
npm install --only=production
cd ../deb/sid
make deb

The output will be sid_1.0.0_all.deb in sid/deb. Copy to your Raspberry Pi and install with:

sudo dpkg -i sid_1.0.0_all.deb

Please note that your Pi will need internet access for installation because the Debian package will automatically install the appropriate version of Node.js for the service. (The installation is sandboxed and will not interfere with any other Node.js installations you may have.)


SID comes preconfigured with the default options used in the previously mentioned article. If you wish to change one or more of those options, after installation, run:

sudo dpkg-reconfigure sid

Follow the prompts for configuration. You may also edit the configuration by hand by editing /opt/sid/src/.env. If you edit by hand, remember to restart the service with:

sudo service sid restart


By default the service listens on port 4253 and presents the following API.


Returns an array of requests for IP addresses that have no static entry in the configuration file. Array entries are in the form:

    "ts": <Date timestamp string>,
    "mac" <MAC address string in the form 11:22:33:44:55:66>

URL: /requests

Method: GET

Success Response:

  • Code: 200
  • Content: [{ ts: '2017-04-24T15:43:28.607Z', mac: '11:22:33:44:55:66'}, ...]


$ curl


Adds a static reservation for the specified MAC address with an optional host name.

URL: /requests/:mac

Method: POST

URL Params:

  • :mac (required) form: 11:22:33:44:55:66 - specifies the MAC address to assign an IP to

Data Params:

  • hostname (optional) - specifies the hostname to assign to the device
    { "hostname": "foo" }

Success Response:

  • Code: 200
  • Content: {"mac":"11:22:33:44:55:66","ip":"","hostname":"phone"}

Error Response:

  • Code: 500
  • Content: {"error":"Error: MAC address is already assigned an address"}


$ curl -H "Content-Type: application/json" -d '{"hostname": "phone"}' -X POST

$ curl -H "Content-Type: application/json" -d '{"hostname": "phone"}' -X POST
{"error":"Error: MAC address is already assigned an address"}


Tells SID to not assign an IP address for the specified MAC. SID will remove the request from the list of outstanding requests, however a new request may be added back if the device re-requests an address after they deny operation.

URL: /requests/:mac

Method: DELETE

URL Params:

  • :mac (required) form: 11:22:33:44:55:66 - specifies the MAC address request to remove

Success Response:

  • Code: 200
  • Content: {}

Error Response:

  • Code: 404
  • Content: {"error":"Not found"}
  • Description: The specified MAC address request was not found in the list of outstanding requests
  • Code: 500
  • Content: {"error":"Error: Server error"}
  • Description: Something went wrong internally with the server. Check the server logs


$ curl -X DELETE

$ curl -X DELETE
{"error":"Not found"}