Check DNS Load Balancer Records

DNS load balancers respond to queries with one or more of the DNS records that they are configured to split the load between. This is done to distribute load between multiple servers, provide redundancy and/or reduce latency.

DNS Check supports monitoring A record (IPv4), AAAA record (IPv6) and CNAME record (IPv4 and/or IPv6) based load balancers. It will notify you if a record becomes unresolvable, or starts resolving to the wrong addresses.

This functionality is available for paid accounts only.

Load Balancer Logic

DNS Check compares the list of IP addresses or domain names that you enter to the records returned in response to a DNS query. If the records returned are either a subset or exact match of those that were entered, the check passes.

If any of the records returned in response to the DNS query were not entered into DNS Check, the check fails.

The order in which records are entered into DNS Check and returned in response to queries does not matter.


Here are the fields that make up a DNS load balancer record:

Field Description Example
Name A fully qualified domain name (FQDN).
Type The DNS record type. Set to "A" for IPv4, "AAAA" for IPv6, or "CNAME". A
Addresses A comma delimited set of IP addresses or domain names. A minimum of 1 and a maximum of 10 may be entered per monitored load balancer,,

DNS Zone File Examples

Here's an example of how an A record load balancer could look in a DNS zone file:

; Name                   Type  Address A A A

If the above zone file is imported into the BIND DNS server, then it will respond to queries for the DNS record with all three records shown above sorted in random order.

DNS servers can also be configured to use different load balancing logic. For example, a load balancer might be configured to only return records that point to healthy servers, randomly return one of its records for each request, or deterministically return records based on the querying IP address' geographic location.

Additional Resources

Sign Up For a Free Account

Free accounts can check up to 10 DNS records at a time. You can always upgrade to a paid account later.