It is commonly useful to configure multiple answers for a given domain name and record type. Due to the behavior of public resolvers this can offer a very simple "round robin" like behavior.
Multiple A record responses
One typical example is if you have multiple webservers, each with a different IP address, that should serve traffic for a given domain. Say you have a domain, www.example.web, and you want to send traffic to three IP addresses: 188.8.131.52, 184.108.40.206, and 220.127.116.11.
- In the NS1 portal, go to the appropriate zone (in this case, example.web) and click Add Record.
- Set the correct domain (www.example.web) and record type (A). You can enter the first answer 18.104.22.168 in the space provided.
- Click the Add Answer button to add the other two answers to the record and Save Changes.
If you do a DNS lookup for the domain (e.g., dig A @dnsX.pYY.nsone.net www.example.web) where "dnsX.pYY.nsone.net" is one of the nameservers listed under the Nameservers tab in your zone, you should get all three answers in the response.
Multiple MX record responses
Another typical example is configuring MX (mail exchange) records for your zone. It is common to specify multiple mail servers, each with a different priority value. For example, maybe you want to set MX for example.web to mail1.example.web with priority 1 (higher), and mail2.example.web with priority 5 (lower).
Follow the same process as for A records, but create an MX record instead. On the record creation page, click Add Answer to add the "mail2" answer. Since the record is an MX record, you'll be prompted to enter both a DNS name and a priority value.
Saving the changes and performing a query on the new record type (dig MX @dnsX.pYY.nsone.net example.web) and you should see both answers.
Other record types and advanced configuration
You can follow a similar process to configure multiple answers for records of any type. You can also experiment with adding Filter Chains on the detailed record config page to manipulate the list of answers. For example, try adding the Shuffle filter to an A record with multiple answers. The answers will be returned in randomized order -- true round robin.