Knowledgebase: DNS
GeoDNS Services Explained
Posted by Devon Roberts on 25 April 2017 01:34 PM
Constellix DNS offers the most advanced GeoDNS services in the industry; Geo Proximity, IP Filters, and Global Traffic Director services. Here is a short example of how these services can be used together for optimal traffic routing.

You can locate our guides for configuration of GeoDNS services at the link below:
http://help.constellix.com/geo-dns/

With IP Filter's the request comes in from the resolving name server and based on the IP of the resolving name server - a configured rule is used for resolution.

With Geo Proximity the request comes in from the resolving name server and based on the IP of the resolving name server - the client location is judged to be "closest to" one of the proximity rules.

If a resolving name server supports EDNS client subnet - the original client IP is passed in the request and used in place of the IP of the resolving name server.

If only one Geo Proximity rule is set up, there is no comparison to make as the resolving name server IP will always be closet to the single rule. Multiple rules must be used at all times when setting up Geo Proximity.

Geo Filters are preferred first over Geo Proximity if used together. For example imagine the following IP Filters:
World 4.4.4.4
NYC 5.5.5.5

With the following Proximity Rules:
Closest to San Jose 6.6.6.6
Closest to Miami 7.7.7.7

A request comes in from a resolving name server 8.8.8.8 located in LA, since it does not match the World or NYC Geo Filters, it uses the Proximity rule for San Jose. A request from Philadelphia would match the NYC IP Filter.

You would add GTD services to the mix to correct outliers. If the following IP Filter rules are present:
UK 7.7.7.7
NYC 1.1.1.1
Florida 2.2.2.2
California 4.4.4.4

Assume UK customers start resolving to US IP's, you would enable GTD, create a EUROPE specific region with the following IP Filters:
UK 7.7.7.7
NYC 1.1.1.1
Florida 2.2.2.2
Cali 4.4.4.4

You would then remove the UK IP Filter from the US East and US West regions. This would eliminate that resolution issue.