I tried to update my EC2 settings to stop doing public IPv4 address, which Amazon is going to charge extra for soon. I updated VPC settings etc on the EC2 side, and when Jenkins starts such agent, I myself can successfully connect to it via IPv6. If I uncheck the "Associate Public IP" checkbox, none of existing strategies work anymore: since Jenkins is running not in EC2 itself, I cannot use "Private IP" connection strategy. The error message I see with "Public IP" stategy is "WARNING: Empty host, your host is most likely waiting for an ip address. ", even though the IPv6 was successfully assigned to it.