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It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today.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 in United States
27,014 blocks match, ordered by prefix.
| Prefix | Addresses | Registry | Country | Allocated |
|---|---|---|---|---|
| 192.251.217.0/24 | 256 | ARIN |  US | 19th Jan 1993 |
| 192.251.218.0/24 | 256 | ARIN | US | 19th Jan 1993 |
| 192.251.22.0/24 | 256 | ARIN | US | 18th Nov 1992 |
| 192.251.225.0/24 | 256 | ARIN | US | 22nd Jan 1993 |
| 192.251.23.0/24 | 256 | ARIN | US | 18th Nov 1992 |
| 192.251.232.0/24 | 256 | ARIN | US | 30th Jan 1993 |
| 192.251.233.0/24 | 256 | ARIN | US | 30th Jan 1993 |
| 192.251.234.0/24 | 256 | ARIN | US | 30th Jan 1993 |
| 192.251.235.0/24 | 256 | ARIN | US | 30th Jan 1993 |
| 192.251.236.0/24 | 256 | ARIN | US | 30th Jan 1993 |
| 192.251.237.0/24 | 256 | ARIN | US | 20th Aug 2015 |
| 192.251.24.0/24 | 256 | ARIN | US | 18th Nov 1992 |
| 192.251.25.0/24 | 256 | ARIN | US | 18th Nov 1992 |
| 192.251.3.0/24 | 256 | ARIN | US | 9th Nov 1992 |
| 192.251.31.0/24 | 256 | ARIN | US | 18th Nov 1992 |
| 192.251.33.0/24 | 256 | ARIN | US | 23rd Jan 1995 |
| 192.251.35.0/24 | 256 | ARIN | US | 18th Nov 1992 |
| 192.251.36.0/24 | 256 | ARIN | US | 18th Nov 1992 |
| 192.251.38.0/24 | 256 | ARIN | US | 19th Nov 1992 |
| 192.251.4.0/24 | 256 | ARIN | US | 6th Nov 1992 |
| 192.251.40.0/24 | 256 | ARIN | US | 20th Nov 1992 |
| 192.251.41.0/24 | 256 | ARIN | US | 20th Nov 1992 |
| 192.251.42.0/24 | 256 | ARIN | US | 20th Nov 1992 |
| 192.251.43.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.44.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.45.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.49.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.5.0/24 | 256 | ARIN | US | 6th Nov 1992 |
| 192.251.50.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.59.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.6.0/24 | 256 | ARIN | US | 6th Nov 1992 |
| 192.251.60.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.66.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.67.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.68.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.7.0/24 | 256 | ARIN | US | 6th Nov 1992 |
| 192.251.70.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.71.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.72.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.76.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.77.0/24 | 256 | ARIN | US | 24th Nov 1992 |
| 192.251.78.0/24 | 256 | ARIN | US | 25th Nov 1992 |
| 192.251.79.0/24 | 256 | ARIN | US | 25th Nov 1992 |
| 192.251.8.0/24 | 256 | ARIN | US | 6th Nov 1992 |
| 192.251.80.0/24 | 256 | ARIN | US | 25th Nov 1992 |
| 192.251.81.0/24 | 256 | ARIN | US | 1st Jul 2026 |
| 192.251.84.0/24 | 256 | ARIN | US | 25th Nov 1992 |
| 192.251.85.0/24 | 256 | ARIN | US | 25th Nov 1992 |
| 192.251.86.0/24 | 256 | ARIN | US | 25th Nov 1992 |
| 192.251.88.0/24 | 256 | ARIN | US | 25th Nov 1992 |