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It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today.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 the most unannounced blocks, largest first.
Unannounced blocks in United States
27,034 blocks match, ordered by prefix.
| Prefix | Addresses | Registry | Country | Allocated |
|---|---|---|---|---|
| 204.145.145.0/24 | 256 | ARIN |  US | 9th Jan 1995 |
| 204.145.146.0/24 | 256 | ARIN | US | 9th Jan 1995 |
| 204.145.148.0/24 | 256 | ARIN | US | 9th Jan 1995 |
| 204.145.149.0/24 | 256 | ARIN | US | 9th Jan 1995 |
| 204.145.150.0/24 | 256 | ARIN | US | 9th Jan 1995 |
| 204.145.151.0/24 | 256 | ARIN | US | 9th Jan 1995 |
| 204.145.153.0/24 | 256 | ARIN | US | 9th Jan 1995 |
| 204.145.154.0/24 | 256 | ARIN | US | 9th Jan 1995 |
| 204.145.155.0/24 | 256 | ARIN | US | 9th Jan 1995 |
| 204.145.156.0/24 | 256 | ARIN | US | 9th Jan 1995 |
| 204.145.159.0/24 | 256 | ARIN | US | 11th Jan 1995 |
| 204.145.16.0/20 | 4.1k | ARIN | US | 15th Sept 1994 |
| 204.145.160.0/24 | 256 | ARIN | US | 11th Jan 1995 |
| 204.145.161.0/24 | 256 | ARIN | US | 11th Jan 1995 |
| 204.145.162.0/24 | 256 | ARIN | US | 11th Jan 1995 |
| 204.145.163.0/24 | 256 | ARIN | US | 11th Jan 1995 |
| 204.145.164.0/24 | 256 | ARIN | US | 18th Jan 1995 |
| 204.145.165.0/24 | 256 | ARIN | US | 12th Jan 1995 |
| 204.145.166.0/24 | 256 | ARIN | US | 12th Jan 1995 |
| 204.145.167.0/24 | 256 | ARIN | US | 13th Jan 1995 |
| 204.145.168.0/24 | 256 | ARIN | US | 13th Jan 1995 |
| 204.145.169.0/24 | 256 | ARIN | US | 13th Jan 1995 |
| 204.145.170.0/24 | 256 | ARIN | US | 13th Jan 1995 |
| 204.145.171.0/24 | 256 | ARIN | US | 13th Jan 1995 |
| 204.145.172.0/24 | 256 | ARIN | US | 13th Jan 1995 |
| 204.145.173.0/24 | 256 | ARIN | US | 13th Jan 1995 |
| 204.145.174.0/24 | 256 | ARIN | US | 13th Jan 1995 |
| 204.145.175.0/24 | 256 | ARIN | US | 13th Jan 1995 |
| 204.145.177.0/24 | 256 | ARIN | US | 13th Jan 1995 |
| 204.145.178.0/24 | 256 | ARIN | US | 13th Jan 1995 |
| 204.145.179.0/24 | 256 | ARIN | US | 13th Jan 1995 |
| 204.145.180.0/24 | 256 | ARIN | US | 13th Jan 1995 |
| 204.145.184.0/24 | 256 | ARIN | US | 18th Jan 1995 |
| 204.145.185.0/24 | 256 | ARIN | US | 18th Jan 1995 |
| 204.145.187.0/24 | 256 | ARIN | US | 18th Jan 1995 |
| 204.145.188.0/24 | 256 | ARIN | US | 18th Jan 1995 |
| 204.145.189.0/24 | 256 | ARIN | US | 18th Jan 1995 |
| 204.145.190.0/24 | 256 | ARIN | US | 18th Jan 1995 |
| 204.145.191.0/24 | 256 | ARIN | US | 18th Jan 1995 |
| 204.145.194.0/24 | 256 | ARIN | US | 18th Jan 1995 |
| 204.145.195.0/24 | 256 | ARIN | US | 18th Jan 1995 |
| 204.145.197.0/24 | 256 | ARIN | US | 6th Jul 2026 |
| 204.145.199.0/24 | 256 | ARIN | US | 18th Jan 1995 |
| 204.145.200.0/24 | 256 | ARIN | US | 18th Jan 1995 |
| 204.145.203.0/24 | 256 | ARIN | US | 19th Jan 1995 |
| 204.145.204.0/24 | 256 | ARIN | US | 19th Jan 1995 |
| 204.145.206.0/24 | 256 | ARIN | US | 20th Jan 1995 |
| 204.145.207.0/24 | 256 | ARIN | US | 20th Jan 1995 |
| 204.145.208.0/24 | 256 | ARIN | US | 20th Jan 1995 |
| 204.145.209.0/24 | 256 | ARIN | US | 20th Jan 1995 |