List of the top 20 organizations with the largest IP allocations in Czechia
| Rank | Name | IPv4 addresses | IPv6 /64 networks | AS numbers | Prefixes |
|---|---|---|---|---|---|
| O2 Czech Republic, a.s. | 2,320,128 | 1.25 x 236 | 2 | 115 | |
| Vodafone Czech Republic a.s. | 2,195,200 | 1.06 x 238 | 1 | 95 | |
| T-Mobile Czech Republic a.s. | 1,910,558 | 1.63 x 236 | 3 | 174 | |
| 4 | CESNET z.s.p.o. | 857,088 | 232 | 1 | 23 |
| 5 | ALFA TELECOM s.r.o. | 526,336 | 0 | 1 | 10 |
| 6 | PODA a.s. | 333,824 | 1.5 x 233 | 2 | 27 |
| 7 | CETIN a.s. | 330,496 | 1.13 x 235 | 1 | 11 |
| 8 | Dial Telecom, a.s. | 279,296 | 234 | 4 | 41 |
| 9 | DHL Information Services (Europe) s.r.o | 217,088 | 1.09 x 221 | 1 | 25 |
| 10 | Nej.cz s.r.o. | 184,320 | 1.19 x 236 | 5 | 28 |
| 11 | Nordic Telecom s.r.o | 119,808 | 1.69 x 236 | 4 | 23 |
| 12 | CD-Telematika a.s. | 118,784 | 232 | 1 | 14 |
| 13 | RADIOKOMUNIKACE a.s. | 106,752 | 232 | 1 | 6 |
| 14 | Nordic Telecom Regional s.r.o. | 71,680 | 1.26 x 235 | 7 | 25 |
| 15 | Brno University of Technology | 68,096 | 1.63 x 235 | 2 | 15 |
| 16 | SMART Comp. a.s. | 66,560 | 1.38 x 235 | 1 | 8 |
| 17 | Ipex Ltd. | 63,488 | 232 | 1 | 6 |
| 18 | Master Internet s.r.o. | 59,648 | 1.31 x 236 | 1 | 47 |
| 19 | CASABLANCA INT a.s. | 59,136 | 232 | 1 | 88 |
| 20 | itself s.r.o. | 57,856 | 1.56 x 236 | 1 | 18 |