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It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today.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 |
|---|---|---|---|---|
| 204.26.255.0/24 | 256 | ARIN |  US | 31st May 2011 |
| 204.27.0.0/20 | 4.1k | ARIN | US | 13th May 1994 |
| 204.27.130.0/24 | 256 | ARIN | US | 9th Nov 1994 |
| 204.27.131.0/24 | 256 | ARIN | US | 9th Nov 1994 |
| 204.27.133.0/24 | 256 | ARIN | US | 9th Nov 1994 |
| 204.27.134.0/24 | 256 | ARIN | US | 9th Nov 1994 |
| 204.27.135.0/24 | 256 | ARIN | US | 9th Nov 1994 |
| 204.27.136.0/24 | 256 | ARIN | US | 9th Nov 1994 |
| 204.27.137.0/24 | 256 | ARIN | US | 9th Nov 1994 |
| 204.27.139.0/24 | 256 | ARIN | US | 9th Nov 1994 |
| 204.27.141.0/24 | 256 | ARIN | US | 9th Nov 1994 |
| 204.27.142.0/24 | 256 | ARIN | US | 9th Nov 1994 |
| 204.27.144.0/24 | 256 | ARIN | US | 9th Nov 1994 |
| 204.27.145.0/24 | 256 | ARIN | US | 9th Nov 1994 |
| 204.27.146.0/24 | 256 | ARIN | US | 9th Nov 1994 |
| 204.27.148.0/24 | 256 | ARIN | US | 2nd Jul 2026 |
| 204.27.150.0/24 | 256 | ARIN | US | 10th Nov 1994 |
| 204.27.151.0/24 | 256 | ARIN | US | 10th Nov 1994 |
| 204.27.152.0/24 | 256 | ARIN | US | 10th Nov 1994 |
| 204.27.154.0/24 | 256 | ARIN | US | 10th Nov 1994 |
| 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 |
| 204.27.180.0/24 | 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 |