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CoreDNS-GSLB: GeoIP Setup & Configuration

This guide explains how to set up geographic routing in CoreDNS-GSLB using either MaxMind GeoIP2 databases or custom subnet location maps.

To use GeoIP-based routing, you must configure either geoip_maxmind or geoip_custom in your Corefile. GSLB will then route queries to the nearest backends using the matching logic defined in the selection modes (see Selection & Failover).

MaxMind Databases

CoreDNS-GSLB supports MaxMind GeoIP2 Country, City, and ASN databases to automatically detect the client's location and match it against the backend pool attributes.

To download the .mmdb files from MaxMind and configure their paths in the gslb block of your Corefile, please refer to the GeoIP Settings in the Corefile Reference.

Custom Location Mapping

If you run an internal network or want to override public GeoIP locations for specific IP subnets, you can use a custom location mapping file.

To enable this by pointing to a YAML mapping file in your Corefile, please refer to the GeoIP Settings in the Corefile Reference.

Custom Mapping File (location_map.yml)

Create a YAML file mapping subnets to custom location tags:

subnets:
  - subnet: "10.0.0.0/24"
    location: ["eu-west-1"]
  - subnet: "192.168.1.0/24" 
    location: ["us-east-1"]

GSLB will map incoming client IPs belonging to these subnets to the defined location tag and direct traffic to backends tagged with the same location value.

Complete Backend Configuration Example

Below is an example of a backend definition demonstrating all available GeoIP location attributes, active healthcheck configuration, and bypass options:

- address: "172.16.0.12"
  continent: "EU"
  country: "FR"
  subdivision: "IDF"
  city: "Paris"
  asn: "12345"
  location: "eu-west-1"
  enable: true
  assume_healthy: true  # Optional: bypasses healthchecks and treats this backend as permanently UP
  priority: 1
  healthchecks:
    - type: grpc
      params:
        port: 9090
        service: ""
        timeout: 5s

Location Matching Fields Reference

  • continent: The exact MaxMind continent code (e.g. AF, AN, AS, EU, NA, OC, SA).
  • country: Two-letter ISO country code (e.g., FR, US, CN).
  • subdivision: Subdivision ISO code (e.g., IDF for Île-de-France, CA for California).
  • city: City name (matched case-insensitively, English name returned by MaxMind database, e.g., Paris, Oakland).
  • asn: Autonomous System Number as a string (e.g., 12345).
  • location: The custom location tag (matching subnets in location_map.yml).