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. | 2,767,104 | 1.48 x 238 | 11 | 170 | |
| Vodafone Czech Republic a.s. | 2,295,808 | 1.45 x 238 | 1 | 107 | |
| T-Mobile Czech Republic a.s. | 1,206,272 | 1.25 x 236 | 4 | 48 | |
| 4 | CESNET z.s.p.o. | 858,368 | 1.13 x 235 | 1 | 29 |
| 5 | ALFA TELECOM s.r.o. | 526,848 | 0 | 1 | 11 |
| 6 | PODA a.s. | 335,104 | 1.5 x 233 | 2 | 31 |
| 7 | Quantcom, a.s. | 276,224 | 234 | 2 | 43 |
| 8 | CETIN a.s. | 264,960 | 1.13 x 235 | 1 | 9 |
| 9 | DHL Information Services (Europe) s.r.o | 224,000 | 1.66 x 221 | 1 | 35 |
| 10 | CD-Telematika a.s. | 117,760 | 232 | 1 | 12 |
| 11 | RADIOKOMUNIKACE a.s. | 106,752 | 232 | 1 | 7 |
| 12 | InterneXt 2000, s.r.o. | 75,776 | 236 | 2 | 13 |
| 13 | Brno University of Technology | 67,840 | 1.63 x 235 | 2 | 14 |
| 14 | STARNET, s.r.o. | 66,048 | 1.69 x 236 | 1 | 29 |
| 15 | Master Internet s.r.o. | 58,880 | 1.31 x 236 | 1 | 46 |
| 16 | ha-vel internet s.r.o. | 51,200 | 232 | 1 | 17 |
| 17 | INTERNET CZ, a.s. | 45,824 | 232 | 1 | 12 |
| 18 | ISP Alliance a.s. | 41,472 | 1.72 x 237 | 10 | 49 |
| 19 | WIA spol. s.r.o. | 40,704 | 232 | 1 | 70 |
| 20 | CoProSys a.s. | 37,888 | 232 | 1 | 13 |