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It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today.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 unannounced space registered through ARIN, largest first.
Unannounced blocks in United States
26,302 blocks match, ordered by prefix.
| Prefix | Addresses | Registry | Country | Allocated |
|---|---|---|---|---|
| 204.145.220.0/24 | 256 | ARIN |  US | 20th Jan 1995 |
| 204.145.221.0/24 | 256 | ARIN | US | 20th Jan 1995 |
| 204.145.222.0/24 | 256 | ARIN | US | 20th Jan 1995 |
| 204.145.223.0/24 | 256 | ARIN | US | 20th Jan 1995 |
| 204.145.224.0/24 | 256 | ARIN | US | 20th Jan 1995 |
| 204.145.227.0/24 | 256 | ARIN | US | 20th Jan 1995 |
| 204.145.228.0/24 | 256 | ARIN | US | 23rd Jan 1995 |
| 204.145.230.0/24 | 256 | ARIN | US | 23rd Jan 1995 |
| 204.145.231.0/24 | 256 | ARIN | US | 23rd Jan 1995 |
| 204.145.233.0/24 | 256 | ARIN | US | 23rd Jan 1995 |
| 204.145.234.0/24 | 256 | ARIN | US | 2nd Jul 2026 |
| 204.145.235.0/24 | 256 | ARIN | US | 23rd Jan 1995 |
| 204.145.236.0/24 | 256 | ARIN | US | 23rd Jan 1995 |
| 204.145.238.0/24 | 256 | ARIN | US | 23rd Jan 1995 |
| 204.145.239.0/24 | 256 | ARIN | US | 24th Jan 1995 |
| 204.145.240.0/24 | 256 | ARIN | US | 24th Jan 1995 |
| 204.145.242.0/24 | 256 | ARIN | US | 24th Jan 1995 |
| 204.145.243.0/24 | 256 | ARIN | US | 24th Jan 1995 |
| 204.145.246.0/23 | 512 | ARIN | US | 24th Jan 1995 |
| 204.145.248.0/23 | 512 | ARIN | US | 24th Jan 1995 |
| 204.145.250.0/24 | 256 | ARIN | US | 27th Jan 1995 |
| 204.145.251.0/24 | 256 | ARIN | US | 27th Jan 1995 |
| 204.145.252.0/23 | 512 | ARIN | US | 30th Jan 1995 |
| 204.145.254.0/24 | 256 | ARIN | US | 30th Jan 1995 |
| 204.147.128.0/20 | 4.1k | ARIN | US | 13th Dec 1994 |
| 204.147.192.0/21 | 2k | ARIN | US | 12th Jan 1995 |
| 204.147.200.0/23 | 512 | ARIN | US | 12th Jan 1995 |
| 204.147.240.0/20 | 4.1k | ARIN | US | 17th Jan 1995 |
| 204.147.64.0/21 | 2k | ARIN | US | 25th Nov 1994 |
| 204.147.72.0/22 | 1k | ARIN | US | 25th Nov 1994 |
| 204.147.96.0/20 | 4.1k | ARIN | US | 9th Dec 1994 |
| 204.15.16.0/22 | 1k | ARIN | US | 2nd Aug 2005 |
| 204.15.168.0/24 | 256 | ARIN | US | 9th Sept 2005 |
| 204.15.170.0/24 | 256 | ARIN | US | 23rd Aug 2011 |
| 204.15.180.0/22 | 1k | ARIN | US | 14th Sept 2005 |
| 204.15.212.0/22 | 1k | ARIN | US | 27th Jul 2020 |
| 204.15.216.0/22 | 1k | ARIN | US | 22nd Sept 2005 |
| 204.15.34.0/23 | 512 | ARIN | US | 17th Apr 2024 |
| 204.15.42.0/24 | 256 | ARIN | US | 21st Jul 2022 |
| 204.15.47.0/24 | 256 | ARIN | US | 8th Jul 2022 |
| 204.15.88.0/21 | 2k | ARIN | US | 17th Aug 2005 |
| 204.152.10.0/23 | 512 | ARIN | US | 23rd Sept 1994 |
| 204.152.106.0/23 | 512 | ARIN | US | 2nd Feb 1995 |
| 204.152.108.0/23 | 512 | ARIN | US | 2nd Feb 1995 |
| 204.152.118.0/23 | 512 | ARIN | US | 21st Feb 1995 |
| 204.152.120.0/23 | 512 | ARIN | US | 28th Feb 1995 |
| 204.152.122.0/23 | 512 | ARIN | US | 28th Feb 1995 |
| 204.152.124.0/23 | 512 | ARIN | US | 28th Feb 1995 |
| 204.152.126.0/23 | 512 | ARIN | US | 1st Mar 1995 |
| 204.152.136.0/23 | 512 | ARIN | US | 4th Mar 1995 |