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It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today.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
26,295 blocks match, ordered by prefix.
| Prefix | Addresses | Registry | Country | Allocated |
|---|---|---|---|---|
| 192.251.161.0/24 | 256 | ARIN |  US | 3rd Dec 1992 |
| 192.251.162.0/24 | 256 | ARIN | US | 3rd Dec 1992 |
| 192.251.165.0/24 | 256 | ARIN | US | 7th Dec 1992 |
| 192.251.167.0/24 | 256 | ARIN | US | 7th Dec 1992 |
| 192.251.168.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.169.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.170.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.171.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.172.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.173.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.176.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.177.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.178.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.179.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.18.0/24 | 256 | ARIN | US | 16th Nov 2018 |
| 192.251.182.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.184.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.185.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.186.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.187.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.188.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.189.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.19.0/24 | 256 | ARIN | US | 16th Nov 1992 |
| 192.251.190.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.191.0/24 | 256 | ARIN | US | 8th Dec 1992 |
| 192.251.192.0/24 | 256 | ARIN | US | 4th Jan 1993 |
| 192.251.20.0/24 | 256 | ARIN | US | 18th Nov 1992 |
| 192.251.203.0/24 | 256 | ARIN | US | 11th Jan 1993 |
| 192.251.208.0/24 | 256 | ARIN | US | 14th Jan 1993 |
| 192.251.209.0/24 | 256 | ARIN | US | 14th Jan 1993 |
| 192.251.21.0/24 | 256 | ARIN | US | 18th Nov 1992 |
| 192.251.210.0/24 | 256 | ARIN | US | 14th Jan 1993 |
| 192.251.211.0/24 | 256 | ARIN | US | 14th Jan 1993 |
| 192.251.212.0/24 | 256 | ARIN | US | 14th Jan 1993 |
| 192.251.214.0/24 | 256 | ARIN | US | 19th Jan 1993 |
| 192.251.215.0/24 | 256 | ARIN | US | 19th Jan 1993 |
| 192.251.216.0/24 | 256 | ARIN | US | 19th Jan 1993 |
| 192.251.217.0/24 | 256 | ARIN | US | 19th Jan 1993 |
| 192.251.218.0/24 | 256 | ARIN | US | 19th Jan 1993 |
| 192.251.22.0/24 | 256 | ARIN | US | 18th Nov 1992 |
| 192.251.225.0/24 | 256 | ARIN | US | 22nd Jan 1993 |
| 192.251.23.0/24 | 256 | ARIN | US | 18th Nov 1992 |
| 192.251.232.0/24 | 256 | ARIN | US | 30th Jan 1993 |
| 192.251.233.0/24 | 256 | ARIN | US | 30th Jan 1993 |
| 192.251.234.0/24 | 256 | ARIN | US | 30th Jan 1993 |
| 192.251.235.0/24 | 256 | ARIN | US | 30th Jan 1993 |
| 192.251.236.0/24 | 256 | ARIN | US | 30th Jan 1993 |
| 192.251.237.0/24 | 256 | ARIN | US | 20th Aug 2015 |
| 192.251.24.0/24 | 256 | ARIN | US | 18th Nov 1992 |
| 192.251.25.0/24 | 256 | ARIN | US | 18th Nov 1992 |