Autonomous System
AS21508 · Comcast Cable Communications, LLC
Overview
AS21508 is announced on the Internet: RIPE RIS route collectors currently see 17 IPv4 prefixes and 61 IPv6 prefixes originated by this network. Together, its IPv4 prefixes cover 70,400 addresses, with overlapping prefixes counted once. In the paths the collectors record, it has 1 upstream neighbour (transit providers or peers) and 51 downstream neighbours (customers or networks it carries). Its most visible upstream is Comcast Cable Communications, LLC (AS7922). AS21508 was assigned by ARIN, and its registration country is United States.
Source: RIPEstat (RIPE NCC), RIS route collectors. Read on October 16, 2026 at 10:56 PM UTC. This page is refreshed at most every 12 hours.
Go further
The trace goes to 141.104.0.1, the first address of 141.104.0.0/16. An address picked inside a prefix may not answer (nothing listens there, or the network filters probes): the trace then shows the path up to the last network that replies.
Announced prefixes
IPv4 prefixes (17 prefixes)
| Prefix | Addresses |
|---|---|
| 50.204.101.0/24 | 256 |
| 50.205.217.0/24 | 256 |
| 50.216.229.0/24 | 256 |
| 50.217.1.0/24 | 256 |
| 50.217.207.0/24 | 256 |
| 50.218.47.0/24 | 256 |
| 50.228.113.0/24 | 256 |
| 50.229.113.0/24 | 256 |
| 50.229.114.0/24 | 256 |
| 50.235.34.0/24 | 256 |
| 141.104.0.0/16 | 65,536 |
| 157.240.147.0/24 | 256 |
| 157.240.148.0/24 | 256 |
| 173.242.174.0/24 | 256 |
| 198.90.112.0/22 | 1,024 |
| 204.194.47.0/24 | 256 |
| 205.223.19.0/24 | 256 |
IPv6 prefixes (61 prefixes)
| Prefix |
|---|
| 2001:559:8a::/48 |
| 2001:559:c0::/48 |
| 2001:559:f7::/48 |
| 2001:559:220::/48 |
| 2001:559:243::/48 |
| 2001:559:280::/48 |
| 2001:559:37d::/48 |
| 2001:559:3ac::/48 |
| 2001:559:3b9::/48 |
| 2001:559:3c8::/48 |
| 2001:559:40a::/48 |
| 2001:559:49a::/48 |
| 2001:559:49b::/48 |
| 2001:559:53c::/48 |
| 2001:559:5c9::/48 |
| 2001:559:5db::/48 |
| 2001:559:72b::/48 |
| 2001:559:73c::/48 |
| 2001:559:788::/48 |
| 2001:559:78a::/48 |
| 2001:559:79d::/48 |
| 2001:559:79e::/48 |
| 2001:559:7a7::/48 |
| 2001:559:7db::/48 |
| 2001:559:804c::/48 |
| 2001:559:81bf::/48 |
| 2001:559:81d7::/48 |
| 2001:559:81d8::/48 |
| 2001:559:8201::/48 |
| 2001:559:82fd::/48 |
| 2001:559:833e::/48 |
| 2001:559:8416::/48 |
| 2001:559:841c::/48 |
| 2001:559:8445::/48 |
| 2001:559:8535::/48 |
| 2001:559:85c1::/48 |
| 2001:559:85ff::/48 |
| 2001:559:8604::/48 |
| 2001:559:871a::/48 |
| 2001:559:875f::/48 |
| 2001:559:8773::/48 |
| 2001:559:87b2::/48 |
| 2001:559:c071::/48 |
| 2001:559:c0f6::/48 |
| 2001:559:c0f7::/48 |
| 2001:559:c10a::/48 |
| 2001:559:c174::/48 |
| 2001:559:c1a5::/48 |
| 2001:559:c1ca::/48 |
| 2001:559:c28f::/48 |
| 2001:559:c290::/48 |
| 2001:559:c2a7::/48 |
| 2001:559:c344::/48 |
| 2001:559:c3e9::/48 |
| 2001:559:c458::/48 |
| 2001:559:c45f::/48 |
| 2001:559:c460::/48 |
| 2001:559:c4db::/48 |
| 2001:559:c4f6::/48 |
| 2001:559:c515::/48 |
| 2001:559:c538::/48 |
Neighbours
Upstreams (transit or peers) (1)
| AS | Network | Visibility |
|---|---|---|
| AS7922 | Comcast Cable Communications, LLC | 7,204 |
Downstreams (customers) (51)
| AS | Network | Visibility |
|---|---|---|
| AS13335 | Cloudflare, Inc. | 503 |
| AS54113 | Fastly, Inc. | 351 |
| AS400114 | Apogee Telecom Inc. | 275 |
| AS396083 | Framatome Inc. | 268 |
| AS36364 | Mary Washington Hospital, Inc. | 266 |
| AS40641 | MGW Telephone Company, Inc. | 263 |
| AS402549 | Terraservers | 260 |
| AS401426 | St. Mary's Medical Center, Inc. | 259 |
| AS54219 | Matthews International Corporation | 258 |
| AS54883 | City of Richmond, Virginia | 258 |
| AS399099 | - | 258 |
| AS32540 | - | 257 |
| AS36040 | Google LLC | 257 |
| AS394058 | - | 257 |
| AS15297 | - | 256 |
| AS399938 | - | 256 |
| AS15173 | - | 253 |
| AS11739 | - | 249 |
| AS394276 | - | 245 |
| AS395772 | - | 234 |
| AS14583 | - | 230 |
| AS36244 | - | 228 |
| AS19923 | - | 222 |
| AS2134 | - | 219 |
| AS397039 | - | 103 |
| AS397483 | - | 40 |
| AS63468 | - | 36 |
| AS393613 | - | 31 |
| AS18773 | - | 23 |
| AS399607 | - | 18 |
The 30 most visible of 51.
Visibility is RIPEstat's count of how often the route collectors observed the link. It compares neighbours with each other; it is not a traffic volume.
How to read this page
An Autonomous System (AS) is a network run under one routing policy: an internet provider, a cloud, a content network, a university. Each one has a number, its ASN, assigned by a regional registry (ARIN, RIPE NCC, APNIC, LACNIC, AFRINIC), and uses BGP, the protocol networks use to tell each other where addresses are, to announce the blocks of addresses it delivers to.
A prefix such as 203.0.113.0/24 is a block of addresses: the number after the slash says how many bits are fixed, so a /24 holds 256 IPv4 addresses and a /16 holds 65,536. Networks often announce a large block and smaller pieces of it at the same time, which is why the address total counts each address once.
Neighbours come from the paths themselves. A network that appears just before this one in a path, on the collector's side, is an upstream: a transit provider or a peer. One that appears just after it is a downstream, usually a customer. Peering at an internet exchange also shows up as an upstream, so the upstream list is not a list of paid transit.
The data comes from RIPEstat, run by the RIPE NCC, which gathers the routing tables of hundreds of networks through its RIS route collectors. This page reads it when it is visited and keeps it for 12 hours at most; the BGP viewer reads it live.