Autonomous system
AS5400 BT
Unclassified RIPE
Summary
BT (British Telecommunications) — European backbone
transit legacy
AS5400 is BT's international IP backbone, the network behind BT.net and BT's global network services business. It is the carrier-side network, distinct from BT's UK consumer and broadband ASNs.
What it's used for
- IP transit and global connectivity for BT's enterprise, wholesale and carrier customers across Europe, North America and Asia.
- Peering with thousands of other networks at major exchanges; the ASN sits near the top of transit-ranking tables.
- Backbone for BT's managed WAN, MPLS and internet products sold outside the UK consumer market.
Notable
- Carrier address, not eyeball address: hosts on AS5400 are far more likely to be enterprise sites, corporate edge routers and infrastructure than home broadband subscribers. BT's UK retail broadband is announced from a separate ASN.
- BT's internet capability is deliberately split by role — a European/global backbone (this ASN), a UK network, and in-country networks in several other European markets. Attributing traffic on AS5400 to "BT home users" is a common mistake.
Interesting
- The network grew out of BT's late-1990s/2000s continental fibre build and the IP business that was branded BT Ignite before becoming BT Global Services.
This description is AI-generated, best-effort context — not authoritative, and provided without any guarantee of accuracy. Source, and how to suggest an edit.
Interconnection
Peering at a glance
Internet exchanges
Recorded at 53 exchanges in 25 countries, largest first.
| Exchange | Location | Their address |
|---|---|---|
| IX.br (PTT.br) São Paulo | São Paulo, Brazil | 187.16.217.237 |
| DE-CIX Frankfurt | Frankfurt, Germany | 80.81.193.84 |
| LINX LON1 | London, United Kingdom | 195.66.224.108 |
| AMS-IX Amsterdam | Amsterdam, Netherlands | 80.249.208.108 |
| Neutral Internet Exchange | Amsterdam, Netherlands | 193.239.117.109 |
| France-IX Paris | Paris, France | 37.49.237.2 |
| Equinix Internet Exchange Singapore | Singapore, Singapore | 27.111.231.53 |
| Milan Internet Exchange | Milan, Italy | 217.29.66.119 |
Transit providers
29 upstream, 61 downstream and 124 adjacent networks observed; most-used upstreams first.
Exchange presence is recorded rather than inferred: the directory collected by Packet Clearing House (https://www.pch.net/ixp/data) on 2026-10-14, licensed CC BY-NC-SA 3.0. Transit is inferred from observed BGP paths, never declared by either party.
Address space
Summary
IPv4 77 prefixes · 713K addresses IPv6 55 prefixes
| Country | Name | Prefixes |
|---|---|---|
| GB | United Kingdom | 132 |
Registry
Allocation record
- Registry
- RIPE
- Handle
AS5400- Registry name
- BT
- Registrant
- CIP-MNT
- Abuse contact
- abuse@eu.bt.net
- Registered
- 2002-08-29
- Last changed
- 2026-03-18
- Allocation
- allocated
Routing security
RPKI and IRR
- RPKI
- 78% valid · 97 valid, 28 with no ROA
- ROAs
- 148 authorising AS5400
- ASPA
- no ASPA record
- IRR
- 100% registered · 125 of 125 announcements
- Route objects
- 277 naming AS5400
Reputation
Classification and threat
Unclassified Not in the curated lists. Most of the ~80,000 allocated ASNs are not.
Spamhaus DROP
Not on ASN-DROP The network as a whole is not listed.
No DROP prefixes None of its announced space is on the DROP prefix list.
Spamhaus DROP ("Don't Route Or Peer") lists space and networks run by, or hijacked for, spam and cybercrime operations: 442 networks and 1,773 prefixes, as published 2026-10-13. A short, high-confidence list, so a match is worth taking seriously, and absence from it says little on its own.
FBI IC3
No IC3 indicators Nothing from the FBI IC3 feed.
IC3 threat data is alpha. Absence of an indicator is not evidence of good behaviour, only of absence from this one feed.
Elsewhere