Wildcard DNS — embed an IP in the hostname, get it back as an A record.
| 1.2.3.4.ip.addre.eu.cc | 1.2.3.4 |
| 1-2-3-4.ip.addre.eu.cc | 1.2.3.4 |
| app.1.2.3.4.ip.addre.eu.cc | 1.2.3.4 |
| app-1-2-3-4.ip.addre.eu.cc | 1.2.3.4 |
| 0x01020304.ip.addre.eu.cc | 1.2.3.4 |
| app.0xc0a80101.ip.addre.eu.cc | 192.168.1.1 |