Is it possible to implement round robin by assigning multiple IP addresses to domain name in DNS service?

Yes. Please register multiple records in the same domain.

As with normal DNS round robin, there is no health check for the registered IP address, so even if the service provided by the specific IP address stops, normal traffic is distributed.

In addition, although ECL 2.0 DNS provides usual DNS round robin, because DNS round robin is realized in cooperation with customer's DNS cache and resolver, please confirm it operates in a state of combining them.