asn.dev

Observed topology

AS21928 T-MOBILE-AS21928

Mobile ARIN

Upstreams 19 carry this network
Downstreams 3 this network carries
Adjacent (IPv4) 22
Adjacent (IPv6) 10
Upstream graph Who carries AS21928, and who carries them, drawn as a map up to the transit-free core. 14 exchanges Where AS21928 physically turns up to peer, and its address on each fabric.

Transit

Upstream networks

All 19

Networks observed carrying traffic for AS21928: the AS immediately before it in a routing path. Ranked by how many paths showed the relationship, which reflects how widely it is used, not how much traffic crosses it.

ASNetworkTypeFamiliesPaths seen
AS174Cogent Communications, LLCTransitIPv4 IPv64,769
AS6939Hurricane Electric LLCTransitIPv4 IPv64,543
AS6461Zayo BandwidthTransitIPv4 IPv63,292
AS3356Level 3 Parent, LLCTransitIPv4 IPv61,221
AS4637Telstra GlobalUnclassifiedIPv4364
AS24482SG.GSHostingIPv4 IPv6285
AS20205Amplex Electric, Inc.ResidentialIPv4215
AS9002RETN LimitedUnclassifiedIPv4 IPv6139
AS7922Comcast Cable Communications, LLCResidentialIPv4124
AS394256Tech Futures Interactive Inc.UnclassifiedIPv4 IPv659

All 19 upstreams →

Transit

Downstream networks

inferred

Networks for which AS21928 was observed as the last hop before the origin, meaning it appears to provide them transit.

ASNetworkTypeFamiliesPaths seen
AS400318Versa Networks, Inc.HostingIPv471
AS22140T-Mobile USA, Inc.UnclassifiedIPv4 IPv662
AS16550Google LLCUnclassifiedIPv43

Adjacency

Adjacent networks

All 22

Every AS seen directly next to AS21928 in a routing path, in either direction.

ASNetworkTypeFamiliesPaths seen
AS174Cogent Communications, LLCTransitIPv4 IPv64,769
AS6939Hurricane Electric LLCTransitIPv4 IPv64,543
AS6461Zayo BandwidthTransitIPv4 IPv63,411
AS3356Level 3 Parent, LLCTransitIPv4 IPv61,221
AS4637Telstra GlobalUnclassifiedIPv4371
AS24482SG.GSHostingIPv4 IPv6285
AS20205Amplex Electric, Inc.ResidentialIPv4222
AS9002RETN LimitedUnclassifiedIPv4 IPv6139
AS7922Comcast Cable Communications, LLCResidentialIPv4127
AS400318Versa Networks, Inc.HostingIPv471

All 22 adjacent →

Provenance

Where this comes from

Derived from routing tables collected at 2026-10-27 10:00 UTC by route-views2,rrc00, as seen from 75 BGP vantage points across 73.06M route entries. These are observations from those vantage points, not a complete or authoritative view of the internet.

Inferred from path position, not from any declaration by either party. A network appearing here is carrying these routes; whether that is a paid transit arrangement, a backup, or something else is not something routing data can tell you. Adjacency is not the same as peering. Being next to each other in a path covers paid transit, settlement-free peering and customer connections alike, and routing data cannot distinguish them. Treat this as "these networks exchange routes", nothing more specific.

Cross-check against RIPEstat or BGP.tools, which observe from a different and larger set of vantage points.