asn.dev

Observed topology

AS5400 BT British Telecommunications Limited

Unclassified RIPE

Upstreams 29 carry this network
Downstreams 63 this network carries
Adjacent (IPv4) 90
Adjacent (IPv6) 35
Upstream graph Who carries AS5400, and who carries them, drawn as a map up to the transit-free core. 52 exchanges Where AS5400 physically turns up to peer, and its address on each fabric.

Transit

Upstream networks

All 29

Networks observed carrying traffic for AS5400: 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
AS1299Arelion Sweden ABTransitIPv4 IPv61,173
AS6939Hurricane Electric LLCTransitIPv4 IPv6974
AS3356Level 3 Parent, LLCTransitIPv4 IPv6835
AS174Cogent Communications, LLCTransitIPv4 IPv6419
AS9002RETN LimitedUnclassifiedIPv4 IPv6411
AS3257GTT Communications Inc.TransitIPv4 IPv6318
AS577Bell CanadaMobileIPv4 IPv6242
AS3491PCCW Global (HK) Ltd.TransitIPv4 IPv6169
AS4637Telstra GlobalUnclassifiedIPv4 IPv6145
AS6762TELECOM ITALIA SPARKLE S.p.A.TransitIPv4 IPv6127

All 29 upstreams →

Transit

Downstream networks

All 63

Networks for which AS5400 was observed as the last hop before the origin, meaning it appears to provide them transit.

ASNetworkTypeFamiliesPaths seen
AS2856British Telecommunications LimitedResidentialIPv4 IPv623,334
AS199541EUROCONTROL, the European Organisation for the Safety of Air NavigationUnclassifiedIPv42,419
AS13205Telecommunications LimitedUnclassifiedIPv4765
AS2110Enet Communications LIMITEDResidentialIPv4 IPv6655
AS33873Arvato Systems GmbHHostingIPv4 IPv6533
AS21489The North Atlantic Treaty OrganizationUnclassifiedIPv4413
AS15442Procter & Gamble Service GmbHUnclassifiedIPv4389
AS21000Atos France SASUnclassifiedIPv4309
AS30614Dell, Inc.UnclassifiedIPv4291
AS29063Eviden Netherlands B.V.UnclassifiedIPv4 IPv6280

All 63 downstreams →

Adjacency

Adjacent networks

All 92

Every AS seen directly next to AS5400 in a routing path, in either direction.

ASNetworkTypeFamiliesPaths seen
AS2856British Telecommunications LimitedResidentialIPv4 IPv636,395
AS1299Arelion Sweden ABTransitIPv4 IPv612,896
AS3356Level 3 Parent, LLCTransitIPv4 IPv610,464
AS6939Hurricane Electric LLCTransitIPv4 IPv66,874
AS174Cogent Communications, LLCTransitIPv4 IPv64,330
AS3257GTT Communications Inc.TransitIPv4 IPv63,535
AS199541EUROCONTROL, the European Organisation for the Safety of Air NavigationUnclassifiedIPv42,419
AS8968RETELIT-X S.R.L.UnclassifiedIPv4 IPv61,817
AS33891Core-Backbone GmbHHostingIPv41,334
AS11164Internet2EducationIPv41,278

All 92 adjacent →

Provenance

Where this comes from

Derived from routing tables collected at 2026-11-13 10:00 UTC by route-views2,rrc00, as seen from 75 BGP vantage points across 74.40M 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.