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It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today.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 the most unannounced blocks, largest first.
Unannounced blocks in United States
27,021 blocks match, ordered by prefix.
| Prefix | Addresses | Registry | Country | Allocated |
|---|---|---|---|---|
| 204.197.208.0/20 | 4.1k | ARIN |  US | 5th Oct 2010 |
| 204.209.255.0/24 | 256 | ARIN | US | 16th Jun 2017 |
| 204.209.66.0/23 | 512 | ARIN | US | 22nd Dec 2020 |
| 204.209.9.0/24 | 256 | ARIN | US | 8th Oct 2025 |
| 204.224.0.0/16 | 65.5k | ARIN | US | 5th Jan 1995 |
| 204.225.120.0/24 | 256 | ARIN | US | 1st Jul 2022 |
| 204.225.133.0/24 | 256 | ARIN | US | 10th Jan 1995 |
| 204.225.172.0/24 | 256 | ARIN | US | 10th Jan 1995 |
| 204.225.239.0/24 | 256 | ARIN | US | 10th Jan 1994 |
| 204.225.38.0/23 | 512 | ARIN | US | 27th Sept 2010 |
| 204.225.52.0/23 | 512 | ARIN | US | 10th Jan 1995 |
| 204.227.160.0/19 | 8.2k | ARIN | US | 23rd Jan 1995 |
| 204.227.32.0/19 | 8.2k | ARIN | US | 12th Jan 1995 |
| 204.227.64.0/19 | 8.2k | ARIN | US | 17th Jan 1995 |
| 204.227.96.0/19 | 8.2k | ARIN | US | 20th Jan 1995 |
| 204.228.160.0/21 | 2k | ARIN | US | 12th Jan 1995 |
| 204.228.168.0/23 | 512 | ARIN | US | 12th Jan 1995 |
| 204.228.170.0/24 | 256 | ARIN | US | 12th Jan 1995 |
| 204.228.171.0/24 | 256 | ARIN | US | 12th Jan 1995 |
| 204.228.172.0/23 | 512 | ARIN | US | 12th Jan 1995 |
| 204.228.174.0/24 | 256 | ARIN | US | 12th Jan 1995 |
| 204.229.0.0/19 | 8.2k | ARIN | US | 12th Jan 1995 |
| 204.229.128.0/18 | 16.4k | ARIN | US | 12th Jan 1995 |
| 204.229.32.0/19 | 8.2k | ARIN | US | 12th Jan 1995 |
| 204.229.64.0/19 | 8.2k | ARIN | US | 12th Jan 1995 |
| 204.229.96.0/19 | 8.2k | ARIN | US | 12th Jan 1995 |
| 204.230.0.0/16 | 65.5k | ARIN | US | 12th Jan 1995 |
| 204.231.192.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 204.231.193.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 204.231.194.0/23 | 512 | ARIN | US | 21st Apr 1995 |
| 204.231.196.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 204.231.197.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 204.231.198.0/23 | 512 | ARIN | US | 21st Apr 1995 |
| 204.231.200.0/21 | 2k | ARIN | US | 21st Apr 1995 |
| 204.231.208.0/20 | 4.1k | ARIN | US | 21st Apr 1995 |
| 204.231.227.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 204.231.229.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 204.231.233.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 204.231.235.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 204.231.236.0/24 | 256 | ARIN | US | 4th May 1995 |
| 204.231.239.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 204.231.242.0/23 | 512 | ARIN | US | 21st Apr 1995 |
| 204.231.244.0/23 | 512 | ARIN | US | 21st Apr 1995 |
| 204.231.246.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 204.231.247.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 204.231.248.0/23 | 512 | ARIN | US | 21st Apr 1995 |
| 204.231.250.0/24 | 256 | ARIN | US | 21st Apr 1995 |
| 204.231.254.0/24 | 256 | ARIN | US | 4th May 1995 |
| 204.232.0.0/18 | 16.4k | ARIN | US | 17th Jan 1995 |
| 204.235.0.0/20 | 4.1k | ARIN | US | 20th Jan 1995 |