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It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today.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 in United States
26,300 blocks match, ordered by prefix.
| Prefix | Addresses | Registry | Country | Allocated |
|---|---|---|---|---|
| 205.166.217.0/24 | 256 | ARIN |  US | 13th Apr 1995 |
| 205.166.218.0/24 | 256 | ARIN | US | 13th Apr 1995 |
| 205.166.219.0/24 | 256 | ARIN | US | 13th Apr 1995 |
| 205.166.220.0/24 | 256 | ARIN | US | 13th Apr 1995 |
| 205.166.221.0/24 | 256 | ARIN | US | 13th Apr 1995 |
| 205.166.222.0/24 | 256 | ARIN | US | 14th Apr 1995 |
| 205.166.223.0/24 | 256 | ARIN | US | 18th Apr 1995 |
| 205.166.224.0/24 | 256 | ARIN | US | 18th Apr 1995 |
| 205.166.225.0/24 | 256 | ARIN | US | 18th Apr 1995 |
| 205.166.227.0/24 | 256 | ARIN | US | 18th Apr 1995 |
| 205.166.228.0/24 | 256 | ARIN | US | 18th Apr 1995 |
| 205.166.229.0/24 | 256 | ARIN | US | 18th Apr 1995 |
| 205.166.23.0/24 | 256 | ARIN | US | 21st Mar 1995 |
| 205.166.232.0/24 | 256 | ARIN | US | 20th Apr 1995 |
| 205.166.233.0/24 | 256 | ARIN | US | 20th Apr 1995 |
| 205.166.234.0/24 | 256 | ARIN | US | 20th Apr 1995 |
| 205.166.235.0/24 | 256 | ARIN | US | 8th Jun 2026 |
| 205.166.236.0/24 | 256 | ARIN | US | 20th Apr 1995 |
| 205.166.237.0/24 | 256 | ARIN | US | 20th Apr 1995 |
| 205.166.238.0/24 | 256 | ARIN | US | 20th Apr 1995 |
| 205.166.239.0/24 | 256 | ARIN | US | 20th Apr 1995 |
| 205.166.24.0/24 | 256 | ARIN | US | 21st Mar 1995 |
| 205.166.240.0/24 | 256 | ARIN | US | 20th Apr 1995 |
| 205.166.242.0/24 | 256 | ARIN | US | 20th Apr 1995 |
| 205.166.243.0/24 | 256 | ARIN | US | 20th Apr 1995 |
| 205.166.244.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 205.166.245.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 205.166.248.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 205.166.249.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 205.166.25.0/24 | 256 | ARIN | US | 21st Mar 1995 |
| 205.166.252.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 205.166.254.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 205.166.27.0/24 | 256 | ARIN | US | 22nd Mar 1995 |
| 205.166.29.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.3.0/24 | 256 | ARIN | US | 17th Mar 1995 |
| 205.166.30.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.31.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.32.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.34.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.38.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.39.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.4.0/24 | 256 | ARIN | US | 17th Mar 1995 |
| 205.166.40.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.41.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.44.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.45.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.46.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.47.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.49.0/24 | 256 | ARIN | US | 23rd Mar 1995 |
| 205.166.5.0/24 | 256 | ARIN | US | 17th Mar 1995 |