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It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today.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 |
|---|---|---|---|---|
| 204.27.200.0/24 | 256 | ARIN |  US | 22nd Nov 1994 |
| 204.27.201.0/24 | 256 | ARIN | US | 16th Jun 1997 |
| 204.27.202.0/24 | 256 | ARIN | US | 23rd Nov 1994 |
| 204.27.204.0/24 | 256 | ARIN | US | 23rd Nov 1994 |
| 204.27.205.0/24 | 256 | ARIN | US | 23rd Nov 1994 |
| 204.27.206.0/24 | 256 | ARIN | US | 25th Nov 1994 |
| 204.27.207.0/24 | 256 | ARIN | US | 28th Nov 1994 |
| 204.27.208.0/24 | 256 | ARIN | US | 28th Nov 1994 |
| 204.27.209.0/24 | 256 | ARIN | US | 28th Nov 1994 |
| 204.27.211.0/24 | 256 | ARIN | US | 30th Nov 1994 |
| 204.27.212.0/24 | 256 | ARIN | US | 30th Nov 1994 |
| 204.27.213.0/24 | 256 | ARIN | US | 2nd Apr 2025 |
| 204.27.214.0/24 | 256 | ARIN | US | 6th Dec 1994 |
| 204.27.215.0/24 | 256 | ARIN | US | 6th Dec 1994 |
| 204.27.216.0/24 | 256 | ARIN | US | 7th Dec 1994 |
| 204.27.218.0/24 | 256 | ARIN | US | 7th Dec 1994 |
| 204.27.220.0/24 | 256 | ARIN | US | 7th Dec 1994 |
| 204.27.223.0/24 | 256 | ARIN | US | 7th Dec 1994 |
| 204.27.225.0/24 | 256 | ARIN | US | 7th Dec 1994 |
| 204.27.226.0/24 | 256 | ARIN | US | 7th Dec 1994 |
| 204.27.228.0/24 | 256 | ARIN | US | 7th Dec 1994 |
| 204.27.230.0/24 | 256 | ARIN | US | 7th Dec 1994 |
| 204.27.232.0/24 | 256 | ARIN | US | 8th Dec 1994 |
| 204.27.234.0/24 | 256 | ARIN | US | 8th Dec 1994 |
| 204.27.235.0/24 | 256 | ARIN | US | 8th Dec 1994 |
| 204.27.236.0/24 | 256 | ARIN | US | 8th Dec 1994 |
| 204.27.238.0/24 | 256 | ARIN | US | 8th Dec 1994 |
| 204.27.240.0/24 | 256 | ARIN | US | 8th Dec 1994 |
| 204.27.241.0/24 | 256 | ARIN | US | 8th Dec 1994 |
| 204.27.242.0/24 | 256 | ARIN | US | 8th Dec 1994 |
| 204.27.243.0/24 | 256 | ARIN | US | 8th Dec 1994 |
| 204.27.245.0/24 | 256 | ARIN | US | 8th Dec 1994 |
| 204.27.246.0/24 | 256 | ARIN | US | 8th Dec 1994 |
| 204.27.247.0/24 | 256 | ARIN | US | 8th Dec 1994 |
| 204.27.248.0/24 | 256 | ARIN | US | 8th Dec 1994 |
| 204.27.251.0/24 | 256 | ARIN | US | 9th Dec 1994 |
| 204.27.252.0/24 | 256 | ARIN | US | 9th Dec 1994 |
| 204.27.253.0/24 | 256 | ARIN | US | 9th Dec 1994 |
| 204.27.254.0/24 | 256 | ARIN | US | 9th Dec 1994 |
| 204.27.255.0/24 | 256 | ARIN | US | 9th Dec 1994 |
| 204.27.32.0/20 | 4.1k | ARIN | US | 18th May 1994 |
| 204.27.48.0/22 | 1k | ARIN | US | 18th May 1994 |
| 204.28.10.0/23 | 512 | ARIN | US | 24th Aug 2011 |
| 204.28.128.0/18 | 16.4k | ARIN | US | 8th Jun 1994 |
| 204.28.192.0/20 | 4.1k | ARIN | US | 8th Jun 1994 |
| 204.28.208.0/21 | 2k | ARIN | US | 10th Jul 2026 |
| 204.28.216.0/22 | 1k | ARIN | US | 21st Jul 2026 |
| 204.28.220.0/23 | 512 | ARIN | US | 8th Jun 1994 |
| 204.28.222.0/24 | 256 | ARIN | US | 17th Jul 2026 |
| 204.28.32.0/19 | 8.2k | ARIN | US | 24th Jun 1994 |