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AS42427Mimecast Services Limited

United KingdomRegistryRIPE NCC

As of 11th November 2026, AS42427 (Mimecast Services Limited), a network registered in the United Kingdom with RIPE NCC, originates 15 IPv4 prefixes covering 3.8k addresses and 2 IPv6 prefixes. By IPv4 address space that makes it the 18,908th-largest of the 80,747 networks we see originating IPv4, and the 577th-largest of 2,122 in the United Kingdom. It is seen behind 3 upstream networks, most often AS6461 (Zayo Bandwidth) and AS3356 (Lumen (Level 3)). 76% of its announcements have a valid RPKI ROA, and none are RPKI-invalid. 76% of its routes reach at least 90% of full-feed peers, and 4 prefixes are also originated by another network.

At a glance

IPv4 prefixes

15

IPv6 prefixes

2

IPv4 addresses

3.8k

IPv6 /64s

131k

Upstream graph

The networks AS42427 is seen behind, one and two hops out, drawn from real AS paths.

AS42427Toward the internet core
Upstream graph for AS42427: 7 neighbouring networks observed beyond it across 2 levels. The same networks are listed in the tables below.AS42427Mimecast Services…This networkAS2914NTT America, Inc.AS3356Lumen (Level 3)AS6461Zayo BandwidthAS49544i3D.net B.VAS215859Hetzner Cloud - S…AS3549Lumen (fka. Globa…AS32590Valve Corporation

Networks observed one and two hops upstream of AS42427 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

7

adjacent networks

Upstreams
343%
Peers
457%
Downstreams
00%

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

Upstreams of AS42427
NetworkCountryRelationshipPathsVantage pts
AS6461Zayo BandwidthUSPeer47475
AS3356Lumen (Level 3)USPeer423108
AS2914NTT America, Inc.USPeer18953

Prefixes

The largest blocks AS42427 originates, widest first.

Largest prefixes originated by AS42427
PrefixAddressesVisibility
41.74.203.0/2425631/76
91.220.42.0/2425676/76
170.10.142.0/2425645/76
185.58.84.0/2425676/76
185.58.85.0/2425676/76
185.58.86.0/2425676/76
185.58.87.0/2425676/76
193.7.204.0/2425676/76
193.7.205.0/2425676/76
195.130.217.0/2425676/76

Routing health

How AS42427'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

  • Valid76.5%13
  • Invalid0.0%0
  • No ROA23.5%4

Propagation

  • Globally propagated90% of full-feed peers or more76.5%13
  • Partially propagated40% to 90%11.8%2
  • Seen by few peersUnder 40%11.8%2

Prefix sizes

IPv4 — 15 prefixes

IPv6 — 2 prefixes

  • /4865.5k × /64100.0%2

Recent changes

Announcements that started or stopped since 12th Oct 2026.

No announcement by AS42427 started or stopped in this period.

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