173.21.0.0/21

Currently announced by AS30036 Mediacom Communications, in the routed prefix 173.21.0.0/21.

Routing data · Nov 8, 2026, 12:23 UTC

ASN historyEvery routed prefix covering 173.21.0.0/21

Prefix	ASN	Name	Registered country	First seen (UTC)	Last seen (UTC)	Status
173.21.0.0/21	AS30036	Mediacom Communications	United States	Before monitoring	2026-11-08 12:23	Announcing

No more specific routes inside this prefix.

Detected (UTC)	Prefix	Change	ASN	Name	Previous ASN	Country
2026-11-03 10:22	173.21.0.0/21	WithdrawalAnnounced again	AS30036	Mediacom Communications	—	United States

From the RIRs’ delegated statistics files. Shows where the addresses are registered, not where they are used.

Every 2 hours ASNBase takes the bgp.tools global routing table (prefix → origin ASN) and compares it with the previous one. The detected time is the time of that comparison; the actual change can be up to about 2 hours earlier.
Only routes seen by more than 100 bgp.tools peers are listed as changes; routes with less visibility are only kept in the history.
A new announcement counts only if it is still in the next routing table, and a withdrawal only if the prefix is missing from two tables in a row, so short flaps are ignored.
ASNBase has been monitoring since 2026-10-19. “Before monitoring” under “First seen” means the route was already announced when monitoring started; the earlier date is unknown.
Prefixes first seen during the first day of monitoring do not count as new announcements: most of them were simply missing from the table at the moment monitoring started.
Countries and regions follow the ASN’s registration, not the actual location of the IP addresses.