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It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today.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
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Countries with unannounced space registered through ARIN, largest first.
Unannounced blocks registered through ARIN
30,476 blocks match, ordered by prefix.
| Prefix | Addresses | Registry | Country | Allocated |
|---|---|---|---|---|
| 204.27.155.0/24 | 256 | ARIN |  US | 10th Nov 1994 |
| 204.27.156.0/24 | 256 | ARIN | US | 10th Nov 1994 |
| 204.27.157.0/24 | 256 | ARIN | US | 14th Nov 1994 |
| 204.27.158.0/24 | 256 | ARIN | US | 15th Nov 1994 |
| 204.27.159.0/24 | 256 | ARIN | US | 15th Nov 1994 |
| 204.27.161.0/24 | 256 | ARIN | US | 15th Nov 1994 |
| 204.27.163.0/24 | 256 | ARIN | US | 16th Nov 1994 |
| 204.27.164.0/24 | 256 | ARIN | US | 16th Nov 1994 |
| 204.27.165.0/24 | 256 | ARIN | US | 16th Nov 1994 |
| 204.27.166.0/24 | 256 | ARIN | US | 16th Nov 1994 |
| 204.27.167.0/24 | 256 | ARIN | US | 16th Nov 1994 |
| 204.27.168.0/24 | 256 | ARIN | US | 16th Nov 1994 |
| 204.27.170.0/24 | 256 | ARIN | US | 16th Nov 1994 |
| 204.27.171.0/24 | 256 | ARIN | US | 16th Nov 1994 |
| 204.27.172.0/24 | 256 | ARIN | US | 16th Nov 1994 |
| 204.27.173.0/24 | 256 | ARIN | US | 16th Nov 1994 |
| 204.27.174.0/24 | 256 | ARIN | US | 2nd Jul 2026 |
| 204.27.175.0/24 | 256 | ARIN | US | 18th Nov 1994 |
| 204.27.176.0/24 | 256 | ARIN | US | 18th Nov 1994 |
| 204.27.177.0/24 | 256 | ARIN | US | 18th Nov 1994 |
| 204.27.179.0/24 | 256 | ARIN |  GB | 20th Feb 1997 |
| 204.27.180.0/24 | 256 | ARIN | US | 18th Nov 1994 |
| 204.27.181.0/24 | 256 | ARIN | US | 18th Nov 1994 |
| 204.27.183.0/24 | 256 | ARIN | US | 21st Nov 1994 |
| 204.27.184.0/24 | 256 | ARIN | US | 21st Nov 1994 |
| 204.27.187.0/24 | 256 | ARIN | US | 21st Nov 1994 |
| 204.27.188.0/24 | 256 | ARIN | US | 22nd Nov 1994 |
| 204.27.189.0/24 | 256 | ARIN | US | 22nd Nov 1994 |
| 204.27.191.0/24 | 256 | ARIN | US | 22nd Nov 1994 |
| 204.27.192.0/24 | 256 | ARIN | US | 22nd Nov 1994 |
| 204.27.193.0/24 | 256 | ARIN | US | 22nd Nov 1994 |
| 204.27.194.0/24 | 256 | ARIN | US | 22nd Nov 1994 |
| 204.27.196.0/24 | 256 | ARIN | US | 22nd Nov 1994 |
| 204.27.198.0/24 | 256 | ARIN | US | 22nd Nov 1994 |
| 204.27.199.0/24 | 256 | ARIN | US | 22nd Nov 1994 |
| 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 |