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. | 2,843,392 | 1.48 x 238 | 10 | 174 | |
| Vodafone Czech Republic a.s. | 2,295,552 | 1.45 x 238 | 1 | 106 | |
| T-Mobile Czech Republic a.s. | 1,178,368 | 1.19 x 236 | 4 | 71 | |
| 4 | CESNET z.s.p.o. | 858,112 | 235 | 1 | 27 |
| 5 | ALFA TELECOM s.r.o. | 526,848 | 0 | 1 | 11 |
| 6 | DHL Information Services (Europe) s.r.o | 438,528 | 1.41 x 222 | 1 | 100 |
| 7 | PODA a.s. | 331,008 | 1.5 x 233 | 2 | 30 |
| 8 | CETIN a.s. | 281,344 | 1.25 x 235 | 2 | 11 |
| 9 | Quantcom, a.s. | 274,432 | 234 | 2 | 41 |
| 10 | CEZNET s.r.o. | 130,304 | 1.09 x 237 | 8 | 38 |
| 11 | CD-Telematika a.s. | 117,760 | 232 | 1 | 12 |
| 12 | RADIOKOMUNIKACE a.s. | 106,752 | 232 | 1 | 7 |
| 13 | STARNET, s.r.o. | 77,312 | 1.09 x 237 | 1 | 33 |
| 14 | Brno University of Technology | 67,840 | 1.63 x 235 | 2 | 14 |
| 15 | MasterDC 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 | WIA spol. s.r.o. | 41,728 | 232 | 1 | 71 |
| 19 | ISP Alliance a.s. | 40,192 | 1.72 x 237 | 8 | 52 |
| 20 | CoProSys a.s. | 37,888 | 232 | 1 | 13 |