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It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today.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.
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Countries with unannounced space registered through ARIN, largest first.
Unannounced blocks in United States
26,302 blocks match, ordered by prefix.
| Prefix | Addresses | Registry | Country | Allocated |
|---|---|---|---|---|
| 204.153.28.0/22 | 1k | ARIN |  US | 5th Oct 1994 |
| 204.153.32.0/23 | 512 | ARIN | US | 10th Oct 1994 |
| 204.153.34.0/24 | 256 | ARIN | US | 10th Oct 1994 |
| 204.153.36.0/23 | 512 | ARIN | US | 17th Oct 1994 |
| 204.153.38.0/24 | 256 | ARIN | US | 17th Oct 1994 |
| 204.153.39.0/24 | 256 | ARIN | US | 2nd Jan 2024 |
| 204.153.4.0/23 | 512 | ARIN | US | 17th Sept 1994 |
| 204.153.44.0/22 | 1k | ARIN | US | 19th Oct 1994 |
| 204.153.6.0/24 | 256 | ARIN | US | 17th Sept 1994 |
| 204.153.64.0/23 | 512 | ARIN | US | 28th Oct 1994 |
| 204.153.66.0/24 | 256 | ARIN | US | 28th Oct 1994 |
| 204.153.68.0/22 | 1k | ARIN | US | 31st Oct 1994 |
| 204.153.72.0/23 | 512 | ARIN | US | 31st Oct 1994 |
| 204.153.84.0/22 | 1k | ARIN | US | 3rd Nov 1994 |
| 204.153.88.0/22 | 1k | ARIN | US | 3rd Nov 1994 |
| 204.153.92.0/22 | 1k | ARIN | US | 8th Nov 1994 |
| 204.154.0.0/21 | 2k | ARIN | US | 21st Sept 1994 |
| 204.154.100.0/23 | 512 | ARIN | US | 17th Oct 1994 |
| 204.154.102.0/23 | 512 | ARIN | US | 1st Nov 2010 |
| 204.154.120.0/24 | 256 | ARIN | US | 19th Oct 1994 |
| 204.154.141.0/24 | 256 | ARIN | US | 21st Dec 2010 |
| 204.154.144.0/22 | 1k | ARIN | US | 25th Oct 1994 |
| 204.154.148.0/23 | 512 | ARIN | US | 25th Oct 1994 |
| 204.154.150.0/24 | 256 | ARIN | US | 25th Oct 1994 |
| 204.154.160.0/21 | 2k | ARIN | US | 26th Oct 1994 |
| 204.154.208.0/21 | 2k | ARIN | US | 15th Nov 1994 |
| 204.154.230.0/23 | 512 | ARIN | US | 3rd Dec 2010 |
| 204.154.232.0/21 | 2k | ARIN | US | 18th Nov 1994 |
| 204.154.32.0/21 | 2k | ARIN | US | 28th Sept 1994 |
| 204.154.72.0/21 | 2k | ARIN | US | 11th Oct 1994 |
| 204.154.88.0/22 | 1k | ARIN | US | 17th Oct 1994 |
| 204.154.92.0/23 | 512 | ARIN | US | 17th Oct 1994 |
| 204.154.96.0/22 | 1k | ARIN | US | 17th Oct 1994 |
| 204.155.80.0/21 | 2k | ARIN | US | 5th Oct 1994 |
| 204.155.88.0/22 | 1k | ARIN | US | 5th Oct 1994 |
| 204.155.92.0/23 | 512 | ARIN | US | 5th Oct 1994 |
| 204.155.94.0/24 | 256 | ARIN | US | 5th Oct 1994 |
| 204.156.178.0/24 | 256 | ARIN | US | 10th Dec 2014 |
| 204.156.32.0/19 | 8.2k | ARIN | US | 28th Sept 1994 |
| 204.16.104.0/22 | 1k | ARIN | US | 27th Oct 2005 |
| 204.16.116.0/22 | 1k | ARIN | US | 22nd Aug 2012 |
| 204.16.152.0/21 | 2k | ARIN | US | 3rd Nov 2005 |
| 204.16.16.0/22 | 1k | ARIN | US | 22nd Nov 2005 |
| 204.16.208.0/22 | 1k | ARIN | US | 20th Mar 2009 |
| 204.16.72.0/22 | 1k | ARIN | US | 30th Sept 2025 |
| 204.17.0.0/21 | 2k | ARIN | US | 9th May 1994 |
| 204.17.128.0/23 | 512 | ARIN | US | 8th Jun 1994 |
| 204.17.138.0/24 | 256 | ARIN | US | 8th Jun 1994 |
| 204.17.141.0/24 | 256 | ARIN | US | 9th Jun 1994 |
| 204.17.145.0/24 | 256 | ARIN | US | 9th Jun 1994 |