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AS203Level 3 Parent, LLC

United StatesRegistryARIN

As of 11th November 2026, AS203 (Level 3 Parent, LLC), a network registered in the United States with ARIN, originates 148 IPv4 prefixes covering 328k addresses and 1 IPv6 prefix. By IPv4 address space that makes it the 942nd-largest of the 80,747 networks we see originating IPv4, and the 241st-largest of 18,752 in the United States. It is seen behind 1 upstream network, most often AS3356 (Lumen (Level 3)). 10% of its announcements have a valid RPKI ROA; 1 is RPKI-invalid. 64% of its routes reach at least 90% of full-feed peers, and 43 prefixes are also originated by another network.

At a glance

IPv4 prefixes

148

IPv6 prefixes

1

IPv4 addresses

328k

IPv6 /64s

4.3B

Upstream graph

The networks AS203 is seen behind, one and two hops out, drawn from real AS paths.

AS203Toward the internet core
Upstream graph for AS203: 3 neighbouring networks observed beyond it across 2 levels. The same networks are listed in the tables below.AS203Level 3 Parent, L…This networkAS3356Lumen (Level 3)AS2914NTT America, Inc.AS3549Lumen (fka. Globa…

Networks observed one and two hops upstream of AS203 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

3

adjacent networks

Upstreams
133%
Peers
267%
Downstreams
00%

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

Upstreams of AS203
NetworkCountryRelationshipPathsVantage pts
AS3356Lumen (Level 3)USPeer8,17078

Prefixes

All 149

The largest blocks AS203 originates, widest first.

Largest prefixes originated by AS203
PrefixAddressesVisibility
149.21.0.0/1665.5k75/76
170.46.0.0/1665.5k32/76
143.112.0.0/1732.8k75/76
143.112.128.0/1816.4k75/76
206.203.64.0/1816.4k75/76
143.112.192.0/198.2k75/76
143.112.224.0/198.2k75/76
156.42.0.0/198.2k76/76
156.42.32.0/198.2k76/76
156.42.64.0/198.2k76/76

Routing health

How AS203'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

  • Valid10.1%15
  • Invalid0.7%1
  • No ROA89.3%133

Propagation

  • Globally propagated90% of full-feed peers or more63.8%95
  • Partially propagated40% to 90%14.8%22
  • Seen by few peersUnder 40%21.5%32

Prefix sizes

IPv4 — 148 prefixes

IPv6 — 1 prefixes

  • /324.3B × /64100.0%1

Recent changes

Announcements that started or stopped since 12th Oct 2026.

25 announced and 57 withdrawn in all; the most recent are shown.

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