Allocated but unannounced space
Every block here was allocated or assigned by a regional internet registry, and none of them appeared in any routing table we collected at our last snapshot — neither as a route of their own, nor covered by a larger announcement, nor carved up into more specifics.
“Unannounced” does not mean “unused”
Plenty of allocated space is deliberately kept off the public internet: private interconnects, lab and lawful-intercept ranges, networks reachable only inside one operator, and space held in reserve. Some of it is announced somewhere our collectors cannot see, which is a limit of our vantage points rather than a fact about the block.
It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today. Nothing on this page means a block is unallocated, available, or free to announce.
Browse by registry
Browse by country
Countries with the most unannounced blocks, largest first.
Unannounced blocks
85,201 blocks match, ordered by prefix.
| Prefix | Addresses | Registry | Country | Allocated |
|---|---|---|---|---|
| 192.251.107.0/24 | 256 | ARIN |  US | 27th Nov 1992 |
| 192.251.108.0/24 | 256 | ARIN | US | 9th Apr 2026 |
| 192.251.11.0/24 | 256 | ARIN | US | 9th Nov 1992 |
| 192.251.110.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.112.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.113.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.114.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.115.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.116.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.117.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.118.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.119.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.12.0/24 | 256 | ARIN | US | 9th Nov 1992 |
| 192.251.120.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.121.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.122.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.123.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.124.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.125.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.126.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.127.0/24 | 256 | ARIN | US | 2nd Apr 2026 |
| 192.251.129.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.130.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.131.0/24 | 256 | ARIN | US | 27th Nov 1992 |
| 192.251.132.0/22 | 1k | ARIN | US | 30th Nov 1992 |
| 192.251.136.0/24 | 256 | ARIN | US | 30th Nov 1992 |
| 192.251.137.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.138.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.143.0/24 | 256 | ARIN | US | 2nd Jun 1995 |
| 192.251.144.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.145.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.146.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.147.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.148.0/24 | 256 | APNIC |  AU | 11th Feb 2011 |
| 192.251.150.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.151.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.152.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.153.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.154.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.155.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.156.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.157.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.158.0/24 | 256 | ARIN | US | 3rd Oct 2024 |
| 192.251.16.0/24 | 256 | ARIN | US | 16th Nov 1992 |
| 192.251.160.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.161.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.162.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.165.0/24 | 256 | ARIN | US | 7th Dec 1992 |
| 192.251.166.0/24 | 256 | ARIN |  CA | 7th Dec 1992 |
| 192.251.167.0/24 | 256 | ARIN | US | 7th Dec 1992 |