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AS51561ICUK Computing Services Limited

United KingdomRegistryRIPE NCCTypeEyeball

As of 12th November 2026, AS51561 (ICUK Computing Services Limited), an access network registered in the United Kingdom with RIPE NCC, originates 76 IPv4 prefixes covering 80.2k addresses and 2 IPv6 prefixes. By IPv4 address space that makes it the 2,829th-largest of the 80,805 networks we see originating IPv4, and the 73rd-largest of 2,122 in the United Kingdom. It is seen behind 36 upstream networks, most often AS2914 (NTT America, Inc.) and AS13335 (Cloudflare, Inc.), and in front of 3 downstream networks. 10% of its announcements have a valid RPKI ROA, and none are RPKI-invalid. 95% of its routes reach at least 90% of full-feed peers.

At a glance

IPv4 prefixes

76

IPv6 prefixes

2

IPv4 addresses

80.2k

IPv6 /64s

4.3B

Upstream graph

The networks AS51561 is seen behind, one and two hops out, drawn from real AS paths.

AS51561Toward the internet core
Upstream graph for AS51561: 12 neighbouring networks observed beyond it across 2 levels. The same networks are listed in the tables below.AS51561ICUK Computing Se…This networkAS174Cogent Communicat…AS2914NTT America, Inc.AS3356Lumen (Level 3)AS6939Hurricane Electri…AS13335Cloudflare, Inc.AS1299Arelion (fka. Tel…AS151326DCConnect Communi…AS49544i3D.net B.VAS215859Hetzner Cloud - S…AS3549Lumen (fka. Globa…AS20130Depaul UniversityAS132337Axclusive

Networks observed one and two hops upstream of AS51561 in real AS paths. A thicker line means more vantage points saw that adjacency, so weight tracks how well attested it is — not how much traffic it carries. Adjacency is an observation; whether it is a transit purchase or a settlement-free peering is an inference, and is labelled as one wherever we show it.

Neighbouring networks

157

adjacent networks

Upstreams
3623%
Peers
11875%
Downstreams
32%

Networks carrying this one's traffic toward the rest of the internet.

Upstreams of AS51561
NetworkCountryRelationshipPathsVantage pts
AS2914NTT America, Inc.USPeer1,66847
AS13335Cloudflare, Inc.USPeer95078
AS3356Lumen (Level 3)USPeer86682
AS174Cogent Communications, LLCUSPeer81190
AS6939Hurricane Electric LLCUSPeer20837
AS25091IP-Max SACHPeer923
AS18106Viewqwest Pte LtdSGPeer902
AS5413Wavenet LimitedGBPeer722
AS8455atom86 BVNLPeer612
AS52075Wifirst S.A.S.FRPeer602

Prefixes

All 78

The largest blocks AS51561 originates, widest first.

Largest prefixes originated by AS51561
PrefixAddressesVisibility
46.33.128.0/198.2k78/78
46.102.192.0/198.2k78/78
80.209.128.0/198.2k78/78
188.240.160.0/198.2k78/78
205.157.160.0/198.2k78/78
80.95.192.0/204.1k78/78
80.209.160.0/204.1k78/78
138.124.128.0/204.1k78/78
80.209.176.0/212k78/78
2.56.84.0/221k78/78

Routing health

How AS51561's own announcements validate against RPKI and how far they propagate. The same measures for the whole routing table are on the routing table in numbers.

RPKI origin validation

  • Valid10.3%8
  • Invalid0.0%0
  • No ROA89.7%70

Propagation

  • Globally propagated90% of full-feed peers or more94.9%74
  • Partially propagated40% to 90%0.0%0
  • Seen by few peersUnder 40%5.1%4

Prefix sizes

IPv4 — 76 prefixes

IPv6 — 2 prefixes

  • /324.3B × /6450.0%1
  • /4865.5k × /6450.0%1

Recent changes

Announcements that started or stopped since 14th Oct 2026.

Routing data derived from RouteViews MRT archives, BGPKIT relationship inference and public registry data.