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. | 2,308,608 | 1.5 x 235 | 2 | 110 | |
| Vodafone Czech Republic a.s. | 2,296,576 | 1.44 x 238 | 1 | 107 | |
| T-Mobile Czech Republic a.s. | 1,355,520 | 1.31 x 236 | 3 | 64 | |
| 4 | CESNET z.s.p.o. | 857,088 | 1.13 x 235 | 1 | 24 |
| 5 | ALFA TELECOM s.r.o. | 526,337 | 0 | 1 | 11 |
| 6 | Nej.cz s.r.o. | 335,616 | 1.78 x 237 | 8 | 65 |
| 7 | PODA a.s. | 333,824 | 1.5 x 233 | 2 | 27 |
| 8 | CETIN a.s. | 330,496 | 1.13 x 235 | 1 | 11 |
| 9 | Quantcom, a.s. | 275,456 | 234 | 3 | 40 |
| 10 | DHL Information Services (Europe) s.r.o | 217,856 | 1.09 x 221 | 1 | 27 |
| 11 | Nordic Telecom Regional s.r.o. | 190,464 | 1.16 x 237 | 11 | 49 |
| 12 | CD-Telematika a.s. | 118,272 | 232 | 1 | 13 |
| 13 | RADIOKOMUNIKACE a.s. | 106,752 | 232 | 1 | 6 |
| 14 | Brno University of Technology | 68,096 | 1.63 x 235 | 2 | 15 |
| 15 | Ipex Ltd. | 62,464 | 232 | 1 | 6 |
| 16 | Master Internet s.r.o. | 59,136 | 1.31 x 236 | 1 | 46 |
| 17 | STARNET, s.r.o. | 55,040 | 1.06 x 236 | 1 | 21 |
| 18 | ha-vel internet s.r.o. | 52,992 | 232 | 1 | 16 |
| 19 | INTERNET CZ, a.s. | 46,080 | 232 | 1 | 13 |
| 20 | ADAPTIVITY s.r.o. | 41,984 | 0 | 1 | 4 |