Split-brain DNS, also known as split-horizon DNS or split-view DNS, is a technique used in computer networking to manage how computers resolve domain names (like cloud.mydomain.tld) differently depending on whether they are inside or outside a specific network, typically an internal network.
as you see in the image
- client from the internet resolve you public DNS name to a public IP address of your router/firewall which in turn sends all requests to an internal system using port forwarding
- clients from internal network resolve the public DNS name to an internal IP address of the application avoiding the loop through the public DNS server, public IP and possible up-/download limits of the external connection
how it works:
- Two sets of DNS records: splitbraindns provides two different sets of DNS records is for internal users on the intrelnal network, and the other is for external users on the internet.
- Implementation: Split-brain DNS can be implemented in a couple of ways:
- Multiple DNS servers: Traditionally, separate external and internal DNS servers were used for internal and external requests.
- DNS policies: Modern DNS servers allow for creating policies that define how to answer requests based on the source address.
There are different methods to implement Split-brain DNS. Most common in self-hosting is a local DNS server which could be integrated into your router or external like popular Pi-Hole pihole or AdguardHome appliances (both offer additional DNS features e.g. advertisement blocking)
more complex view, showing internal and external DNS server…