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It is also a snapshot, not a history: a block announced yesterday and withdrawn this morning appears here today.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 Japan
1,438 blocks match, ordered by prefix.
| Prefix | Addresses | Registry | Country | Allocated |
|---|---|---|---|---|
| 192.51.236.0/24 | 256 | APNIC |  JP | 6th Aug 1993 |
| 192.51.237.0/24 | 256 | APNIC | JP | 6th Aug 1993 |
| 192.51.238.0/24 | 256 | APNIC | JP | 6th Aug 1993 |
| 192.51.239.0/24 | 256 | APNIC | JP | 6th Aug 1993 |
| 192.51.241.0/24 | 256 | APNIC | JP | 6th Aug 1993 |
| 192.51.242.0/24 | 256 | APNIC | JP | 6th Aug 1993 |
| 192.51.243.0/24 | 256 | APNIC | JP | 6th Aug 1993 |
| 192.51.244.0/24 | 256 | APNIC | JP | 6th Aug 1993 |
| 192.51.245.0/24 | 256 | APNIC | JP | 6th Aug 1993 |
| 192.51.246.0/24 | 256 | APNIC | JP | 6th Aug 1993 |
| 192.51.247.0/24 | 256 | APNIC | JP | 6th Aug 1993 |
| 192.51.248.0/24 | 256 | APNIC | JP | 6th Aug 1993 |
| 192.51.249.0/24 | 256 | APNIC | JP | 6th Aug 1993 |
| 192.51.250.0/24 | 256 | APNIC | JP | 7th May 1993 |
| 192.51.251.0/24 | 256 | APNIC | JP | 7th May 1993 |
| 192.51.253.0/24 | 256 | APNIC | JP | 6th Aug 1993 |
| 192.51.255.0/24 | 256 | APNIC | JP | 21st Feb 1989 |
| 192.51.32.0/22 | 1k | APNIC | JP | 2nd Aug 1993 |
| 192.51.36.0/24 | 256 | APNIC | JP | 2nd Aug 1993 |
| 192.51.37.0/24 | 256 | APNIC | JP | 21st Feb 1989 |
| 192.51.38.0/24 | 256 | APNIC | JP | 21st Feb 1989 |
| 192.51.44.0/24 | 256 | APNIC | JP | 2nd Aug 1993 |
| 192.51.45.0/24 | 256 | APNIC | JP | 2nd Aug 1993 |
| 192.51.46.0/24 | 256 | APNIC | JP | 2nd Aug 1993 |
| 192.51.47.0/24 | 256 | APNIC | JP | 2nd Aug 1993 |
| 192.51.49.0/24 | 256 | APNIC | JP | 21st Feb 1989 |
| 192.51.50.0/24 | 256 | APNIC | JP | 21st Feb 1989 |
| 192.51.51.0/24 | 256 | APNIC | JP | 21st Feb 1989 |
| 192.51.52.0/23 | 512 | APNIC | JP | 11th Jul 1994 |
| 192.51.56.0/24 | 256 | APNIC | JP | 12th Oct 2001 |
| 192.51.57.0/24 | 256 | APNIC | JP | 21st Feb 1989 |
| 192.51.58.0/23 | 512 | APNIC | JP | 21st Feb 1989 |
| 192.51.60.0/23 | 512 | APNIC | JP | 21st Feb 1989 |
| 192.51.62.0/24 | 256 | APNIC | JP | 9th Feb 1995 |
| 192.51.63.0/24 | 256 | APNIC | JP | 21st Feb 1989 |
| 192.51.64.0/18 | 16.4k | APNIC | JP | 21st Feb 1989 |
| 192.52.119.0/24 | 256 | APNIC | JP | 24th Jan 2011 |
| 192.52.120.0/21 | 2k | APNIC | JP | 24th Jan 2011 |
| 192.52.128.0/20 | 4.1k | APNIC | JP | 24th Jan 2011 |
| 192.52.144.0/22 | 1k | APNIC | JP | 24th Jan 2011 |
| 192.52.148.0/23 | 512 | APNIC | JP | 24th Jan 2011 |
| 192.52.150.0/24 | 256 | APNIC | JP | 24th Jan 2011 |
| 192.55.118.0/24 | 256 | APNIC | JP | 31st Jul 1989 |
| 193.82.64.0/19 | 8.2k | APNIC | JP | 19th Apr 1995 |
| 194.117.52.128/26 | 64 | RIPE NCC | JP | 21st Aug 2025 |
| 198.28.0.0/22 | 1k | ARIN | JP | 1st Oct 2026 |
| 198.74.24.0/23 | 512 | APNIC | JP | 22nd Feb 1993 |
| 199.43.18.0/24 | 256 | APNIC | JP | 18th Mar 1994 |
| 2001:2a0:2000::/35 | 537M × /64 | APNIC | JP | 18th Nov 2002 |
| 2001:2a0:4000::/34 | 1.1B × /64 | APNIC | JP | 18th Nov 2002 |