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. | 2,318,336 | 1.25 x 236 | 2 | 113 | |
| T-Mobile Czech Republic a.s. | 2,035,869 | 1.16 x 237 | 3 | 356 | |
| CESNET z.s.p.o. | 857,088 | 232 | 1 | 23 | |
| 4 | ALFA TELECOM s.r.o. | 526,336 | 0 | 1 | 10 |
| 5 | PODA a.s. | 333,824 | 1.5 x 233 | 2 | 27 |
| 6 | CETIN a.s. | 330,496 | 1.13 x 235 | 1 | 11 |
| 7 | Vodafone Czech Republic a.s. | 175,872 | 1.06 x 236 | 1 | 14 |
| 8 | Nej.cz s.r.o. | 172,032 | 1.06 x 236 | 3 | 20 |
| 9 | DHL Information Services (Europe) s.r.o | 151,552 | 1.09 x 221 | 1 | 23 |
| 10 | CD-Telematika a.s. | 122,368 | 232 | 1 | 14 |
| 11 | RADIOKOMUNIKACE a.s. | 107,776 | 232 | 1 | 10 |
| 12 | Ipex Ltd. | 71,680 | 232 | 1 | 8 |
| 13 | Libli s.r.o. | 71,680 | 1.26 x 235 | 7 | 25 |
| 14 | Brno University of Technology | 67,840 | 1.63 x 235 | 2 | 14 |
| 15 | SMART Comp. a.s. | 66,560 | 1.25 x 235 | 1 | 8 |
| 16 | Casablanca INT | 61,184 | 1.13 x 235 | 1 | 97 |
| 17 | Master Internet s.r.o. | 59,648 | 1.25 x 236 | 1 | 46 |
| 18 | Fortech s.r.o. | 58,368 | 235 | 1 | 5 |
| 19 | itself s.r.o. | 57,856 | 1.56 x 236 | 1 | 18 |
| 20 | Nordic Telecom s.r.o | 56,320 | 1.13 x 236 | 2 | 15 |