NetBox DNS Bridge

The NetBox DNS Bridge plugin extends NetBox DNS by embedding a lightweight DNS server directly within NetBox. It acts as a bridge between NetBox DNS and your existing DNS infrastructure, leveraging native DNS mechanisms for seamless integration. These include zone transfers (RFC 5936), catalog zones (RFC 9432), and notifying clients about zone changes (RFC 1996).

Plugin configuration

While providing Zone transfers via AXFR, the Server also exposes specialized catalog zones that BIND and other RFC9432 compliant DNS Servers use to automatically discover newly created zones and remove deleted ones. The plugin supports views and basic DNS security via TSIG.

The plugin exposes one catalog zone per view. Each catalog zone is made available under the special zone name "catz" and addtionally under "[viewname].catz" and may be queried through the built-in DNS server just like any other dns zone.

For proper operation, each view requires an installed TSIG key, and the dns-transfer-endpoint must be running as a separate background service using the manage.py command. Note that DNSSEC support will be added once BIND9 provides a mechanism to configure it through the Catalog Zones system.

To start the transfer endpoint service in the foreground:

manage.py dns-transfer-endpoint --port 5354

This process needs to be scheduled as a background service for the built-in DNS Server to work correctly. For Linux users with Systemd (Ubuntu, etc), Matt Kollross provides a startup unit and instructions here.

Service parameters

Plugin settings

Plugin settings should be configured under PLUGINS_CONFIG in netbox_dns_bridge:

PLUGINS_CONFIG = {
    'netbox_dns_bridge': {
        ...
        ...
    }
}

TSIG Authentication

Following sets the TSIG key that allows clients to query the transfer endpoint and also they key to be used to sign NOTIFY messages to clients on zone changes. Each view should have its own unique key to allow the plugin to identify the view the client is trying to access. Re-using the key for multiple views yields unpredicted behavior.

'tsig_keys': {
    'the-view-name-here': {
        'keyname': 'the-tsig-key-name-here',
        'algorithm': 'hmac-sha256',
        'secret': 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'
    }
}

NOTIFY

Clients may be notified of zone changes using the NOTIFY mechanism defined in RFC 1996. When enabled, the zone transfer endpoint keeps track of any client that successfully queried the endpoint. Once a zone has changed, NetBox informs each client about the zone changed so that the client can request a new zone transfer.

Note that this feature uses NetBox's background job system to schedule the messages asynchronously. In order to work, you need at least one rq-worker service running in the background to handle the queued jobs.

NOTIFY Settings

'notify_clients': True

This enables the NOTIFY system. Defaults to False

'notify_client_alive_threshold_hours': 24

This sets how long a client is considred "alive" after it last queried the transfer endpoint. Once the client has failed to check in for this amout of time, it is automatically removed from the list of clients to be notified on zone changes. Default is 24 hours.

'notify_over_tcp': True

Switch to using TCP instead of UDP. Defaults to False

NOTIFY to a zone's own nameservers

In addition to notifying clients that queried the transfer endpoint, the plugin can send a NOTIFY directly to a zone's own nameservers whenever that zone's SOA serial number changes. This is useful when you want nameservers to pull updates immediately, independent of the notify_clients mechanism. Only a change of the SOA serial triggers this — other zone edits that leave the serial untouched do not.

This can be enabled per zone, globally, or both. If neither of the settings below is configured, the feature is disabled entirely.

Per zone (custom field). Create a boolean custom field (e.g. dns_bridge_notify_ns) that applies to netbox_dns > zone, then point the plugin at it:

'notify_ns_custom_field_name': 'dns_bridge_notify_ns'

A NOTIFY is then sent for any zone whose custom field is set to True. This lets you toggle the behavior per zone straight from the NetBox UI, without changing the plugin config.

Globally (all zones).

'notify_ns_all_zones': True

When enabled, a NOTIFY is sent for every zone on serial change, regardless of the custom field. Defaults to False. The two options coexist: a NOTIFY is sent if the global switch is on or the zone's custom field is set.

The nameserver addresses are resolved from NetBox DNS itself by looking up active A/AAAA records (within the zone's view) matching each nameserver's hostname. The NOTIFY messages are signed with the same per-view TSIG key configured under tsig_keys, so the receiving nameservers must accept NOTIFY signed with that key (e.g. BIND's allow-notify { key "..."; };).

'notify_ns_port': 53

Destination port used for these NOTIFY messages. Defaults to 53.

As with the client NOTIFY feature, this uses NetBox's background job system, so at least one rq-worker service must be running.

Plugin compatibility

This plugin extends the netbox-plugin-dns plugin. As such the versioning was changed to match the one of netbox-plugin-dns more closely. To guarantee compatability, ensure that the major and minor version match between both plugins. For example, when using netbox-plugin-dns v1.5.5 install netbox-plugin-dns-bridge v1.5.x.

Installation guide

This setup provisions a BIND9 server directly with DNS data from NetBox. BIND9 can optionally run on a separate server. If so, any reference to 127.0.0.1 in step 6 must be replaced with the IP address of the NetBox host. TCP and UDP traffic from the BIND9 server to the NetBox host must be allowed on port 5354 (or the port you have configured).

This guide assumes:

• NetBox has been installed under /opt/netbox
• Bind9 is installed on the same host as NetBox
• The NetBox DNS Plugin netbox-plugin-dns is installed
• The following dns views exist in NetBox DNS:
  • public (the default)
  • private

1. Preliminaries

   • Install Bind9 on the same host that netbox is on.
   • Generate a TSIG Key for the public and private dns views respectively.

2. Adding required package

   cd netbox
   echo netbox-plugin-dns-bridge >> local_requirements.txt
   . venv/bin/activate
   pip install -r local_requirements.txt
   

3. Updating netbox plugin configuration (configuration.py) Change following line from

   PLUGINS = ['netbox_dns']
   

   to

   PLUGINS = ['netbox_dns', 'netbox_dns_bridge']
   

   Configure the DNS Bridge Plugin using the PLUGINS_CONFIG dictionary. Change

   PLUGINS_CONFIG = {}
   

   to

   PLUGINS_CONFIG = {
       "netbox_dns_bridge": {
           "tsig_keys": {
               "public": {
                   "keyname":   "public_view_key",
                   "algorithm": "hmac-sha256",
                   "secret":    "base64-encoded-secret"
               },
               "private": {
                   "keyname":   "private_view_key",
                   "algorithm": "hmac-sha256",
                   "secret":    "base64-encoded-secret"
               }
           }
       }
   }
   

   Note that the tsig-key attributes keyname, algorithm and secret form a dictionary in following python structure path:

   PLUGINS_CONFIG.netbox_dns_bridge.tsig_keys.<dns_view_name>
   

   This allows the plugin to map requests to the right dns view using the tsig signature from each request.

4. Run migrations

   manage.py migrate
   

5. Start listener

   This step runs the DNS endpoint used by bind to configure itself. You may want to write a service wrapper that runs this in the background. A guide for setting up a systemd service on Ubuntu is provided by Matt Kollross here. Dont forget to activate the venv if you do decide to run this service in the background.

   Note that --port 5354 is optional. The listener will bind this port by default.

   manage.py dns-transfer-endpoint --port 5354
   

6. Configuring a Bind9 to interact with NetBox via the dns-transfer-endpoint endpoint. Note that its not possible to give all the correct details of the options block as it is heavily dependent on the Operating System used. Please dont forget to adjust as required.

   ########## OPTIONS ##########
   
   options {
       allow-update      { none; };
       allow-query       { any; };
       allow-recursion   { none; };
       notify            yes;
       min-refresh-time  60;
   };
   
   ########## ACLs ##########
   
   acl public {
       !10.0.0.0/8;
       !172.16.0.0/12;
       !192.168.0.0/16;
       any;
   };
   
   acl private {
       10.0.0.0/8;
       172.16.0.0/12;
       192.168.0.0/16;
   };
   
   ######## TSIG Keys ########
       key "public_view_key" {
           algorithm hmac-sha256;
           secret "base64-encoded-secret";
       };
   
       key "private_view_key" {
           algorithm hmac-sha256;
           secret "base64-encoded-secret";
       };
   ###########################
   
   
   ########## ZONES ##########
   view "public" {
       match-clients { public; };
       allow-notify { key "public_view_key"; };
   
       catalog-zones {
           zone "catz"
               default-masters { 127.0.0.1 port 5354 key "public_view_key"; }
               zone-directory "/var/lib/bind/zones"
               min-update-interval 1;
       };
   
       zone "catz" {
           type slave;
           file "/var/lib/bind/zones/catz_public";
           masters { 127.0.0.1 port 5354 key "public_view_key"; };
           notify no;
       };
   };
   
   view "private" {
       match-clients { private; };
       allow-notify { key "private_view_key"; };
   
       catalog-zones {
           zone "catz"
               default-masters { 127.0.0.1 port 5354 key "private_view_key"; }
               zone-directory "/var/lib/bind/zones"
               min-update-interval 1;
       };
   
       zone "catz" {
           type slave;
           file "/var/lib/bind/zones/catz_private";
           masters { 127.0.0.1 port 5354 key "private_view_key"; };
           notify no;
       };
   };
   

7. Restart bind - Done