asn.dev

Observed topology

AS21101 SISTEMIUNO-AS ASP - Application Service Provider

Residential RIPE Cable/DSL/ISP

Upstreams 9 carry this network
Downstreams 2 this network carries
Adjacent (IPv4) 11
Adjacent (IPv6) 0
Upstream graph Who carries AS21101, and who carries them, drawn as a map up to the transit-free core. 4 exchanges Where AS21101 physically turns up to peer, and its address on each fabric.

Transit

Upstream networks

inferred

Networks observed carrying traffic for AS21101: 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
AS41327Fiber Telecom S.p.A.ResidentialIPv4820
AS12779IT.Gate S.p.A.UnclassifiedIPv4160
AS6939Hurricane Electric LLCTransitIPv4140
AS3303Swisscom (Schweiz) AGResidentialIPv420
AS20766Association "Gitoyen"UnclassifiedIPv420
AS24482SG.GSHostingIPv420
AS37721Virtual Technologies & SolutionsResidentialIPv420
AS50628Leonix Telecom SASUnclassifiedIPv420
AS59919Brainbox S.r.l.ResidentialIPv420

Transit

Downstream networks

inferred

Networks for which AS21101 was observed as the last hop before the origin, meaning it appears to provide them transit.

ASNetworkTypeFamiliesPaths seen
AS13060Basic Net SpAUnclassifiedIPv458
AS44091SISTEMI SPAUnclassifiedIPv426

Adjacency

Adjacent networks

All 11

Every AS seen directly next to AS21101 in a routing path, in either direction.

ASNetworkTypeFamiliesPaths seen
AS41327Fiber Telecom S.p.A.ResidentialIPv4884
AS12779IT.Gate S.p.A.UnclassifiedIPv4163
AS6939Hurricane Electric LLCTransitIPv4146
AS13060Basic Net SpAUnclassifiedIPv458
AS44091SISTEMI SPAUnclassifiedIPv426
AS3303Swisscom (Schweiz) AGResidentialIPv422
AS20766Association "Gitoyen"UnclassifiedIPv422
AS37721Virtual Technologies & SolutionsResidentialIPv422
AS50628Leonix Telecom SASUnclassifiedIPv422
AS59919Brainbox S.r.l.ResidentialIPv422

All 11 adjacent →

Provenance

Where this comes from

Derived from routing tables collected at 2026-10-31 10:00 UTC by route-views2,rrc00, as seen from 76 BGP vantage points across 74.50M 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.