BT IP Ranges
BT is the incumbent carrier in the UK, and RIPE registers its broadband network as AS2856 under the AS name BT-UK-AS, administered from Adastral Park in Ipswich. It announces fewer than five hundred IPv4 prefixes and only a handful of IPv6 ones.
- Provider
- BT
- Primary ASN
- AS2856
- Category
- ISP
- Headquarters
- London, UK
- Announced IPv4 prefixes
- 490
- Registry
- RIPE
Known IP ranges
These prefixes are currently announced to the global routing table by AS2856 (BT-UK-AS British Telecommunications PLC). Prefix sets change over time - use WHOIS Lookup for the authoritative record on any specific address.
86.128.0.0/10
81.128.0.0/11
86.128.0.0/11
217.32.0.0/12
109.144.0.0/12
81.128.0.0/12
86.128.0.0/12
95.144.0.0/13
31.48.0.0/13
31.100.0.0/14
2a00:2380::/25
2a01:4c8::/29
2a02:ee80:4176::/47 (IPv6)
What does a BT IP mean in a privacy test?
A BT address as your visible IP means the connection left over the BT line itself with nothing tunnelling it. BT's hostnames repeat both the address and the block it was taken from, so one PTR query confirms the range as well - useful when the real question is whether two addresses came out of the same allocation.
Where to get BT's address list
BT publishes no allowlist for its consumer network, so the RIPE database is the source. The aut-num for AS2856 carries the AS name BT-UK-AS and gives British Telecommunications at PP1, Floor 1, Orion, Adastral Park, Martlesham Heath, Ipswich; the object was created on 30 August 2002 and last changed in July 2026. The AS2856 page carries the same record beside the routing data.
The two address families are wildly different sizes here, and that changes how you write a rule. AS2856 announces several hundred IPv4 prefixes against a handful of IPv6 ones, and the IPv6 side includes 2a00:2380::/25 - a single announcement covering an enormous amount of space. An IPv4 list of BT is several hundred lines that need maintaining; the IPv6 equivalent is under ten and will stay that way. If you only need to recognise BT rather than enumerate it, the ASN is the key that survives both.
What a btcentralplus.com hostname tells you
BT names each broadband address after itself and after the block it came from. 86.128.0.1 answers as host86-128-0-1.range86-128.btcentralplus.com: the address in dashes, then range86-128 naming the aggregate it belongs to, then the zone. That second label is the unusual part - most carriers give you the address back and stop - and it means a single PTR query tells you which BT allocation an address sits in without a second lookup against the routing table.
What the name does not do is separate a household from a small business, or say anything about who is behind the line. Both sit in the same zone, and BT publishes no mapping from addresses to accounts. It does settle the other half of the question: AS2856 is access network, not hosting, so an address here is a line rather than a machine somebody rented, and it is not space a proxy service can appear on by buying capacity.
Related tools
Frequently asked questions
What IP ranges does BT use?
BT announces its broadband network under AS2856, which RIPE registers to British Telecommunications under the AS name BT-UK-AS. The largest blocks currently routed there are listed above, among them 86.128.0.0/10 and 81.128.0.0/11. No allowlist is published, so the RIPE database is the checkable source.
Why does a BT IP appear in my privacy test?
A BT address as your visible IP means the connection left over the BT line itself with nothing tunnelling it. BT's hostnames repeat both the address and the block it was taken from, so one PTR query confirms the range as well - useful when the real question is whether two addresses came out of the same allocation.
What does range86-128 mean in a BT hostname?
It names the aggregate the address belongs to. A BT hostname looks like host86-128-0-1.range86-128.btcentralplus.com: the address in dashes, then the block it came from, then the zone. Most carriers give back only the address, so BT's naming answers a second question in the same query.
Why does BT announce so few IPv6 prefixes?
Because they are very large. AS2856 announces several hundred IPv4 prefixes but fewer than ten IPv6 ones, and those include 2a00:2380::/25 - a single announcement covering an enormous amount of address space. Fewer, bigger announcements are the normal shape of a well-aggregated IPv6 deployment.
Is a BT address a residential line?
It is a subscriber line, though the reverse DNS does not separate residential from small-business service - both sit in the btcentralplus.com zone. What it does establish is that AS2856 is access network rather than hosting, so the address is a connection and not a machine somebody leased.