Quiz Entry - updated: 2026.07.14
What is a Unique Local Address (ULA), and what is a common misconception about it?
A ULA (fc00::/7) is used for local addressing within or between a limited number of sites — like IPv4 RFC 1918 private addresses — and is never globally routed or translated to a GUA.
Unique Local Addresses (ULA):
| Property | Detail |
|---|---|
| Range | fc00::/7 (in practice fd00::/8, the half defined for local assignment) |
| Scope | Within a site, or between a limited number of sites |
| Routing | Not globally routed; not translated to a global address |
| Use case | Devices that never need to reach another network |
Common misconception (gotcha):
- Some admins treat ULAs like IPv4 RFC 1918 addresses to "hide" or secure a network. The Cisco material is explicit that this was never the intended purpose of ULAs — privacy/security comes from firewalls and policy, not from the address type.
Contrast with GUA: a GUA is globally unique and Internet-routable; a ULA is locally unique but deliberately non-routable on the global Internet.
Go deeper:
Unique local address (Wikipedia) — fc00::/7, the fd00::/8 locally-assigned half with its random Global ID, and how ULAs differ from RFC 1918.