Avoid collisions between test names and real names
01The Domain Name System (DNS) is a tree of names. A top-level domain, or TLD, is directly below the root. Inventing an unreserved TLD for a lab can collide with global use.
A separate .test lab example uses a name reserved for DNS testing. Its local configuration remains explicit; the name alone does not confine traffic.
Source for this drawing: RFC 2606 · Read RFC section 2 ↗
New to this? Start hereA quick picture + helpful background
A message needs an address.
Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.
Helpful first, if these ideas are unfamiliar
These pictures are analogies to help you learn. The linked RFC explains the actual rules.
Terms in this drawing
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
RFC 2606 reserves .test, .example, .invalid and .localhost for their stated purposes, reducing conflicts with present or future actual TLD names.
- RFC 2606 reserves .test, .example, .invalid and .localhost for their stated purposes, reducing conflicts with present or future actual TLD names.
- An invented TLD that seems unused is not a permanent reservation. Lab data can later shadow global data under the same name.
- A reserved name reduces namespace confusion; it does not isolate software, block network access or supply authentication.
All scenarios are illustrations; this site makes no DNS queries and changes no resolver. RFC 2606 §5 explains that even documentation can become running software. The root is shown as a dot; a final dot in a fully qualified name represents that root.
Read the RFC section ↗