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AS203Level 3 Parent, LLC

United StatesRegistryARIN

As of 27th September 2026, AS203 (Level 3 Parent, LLC), a network registered in the United States with ARIN, originates 175 IPv4 prefixes covering 335k addresses and 1 IPv6 prefix. By IPv4 address space that makes it the 901st-largest of the 79,525 networks we see originating IPv4, and the 225th-largest of 18,428 in the United States. It is seen behind 1 upstream network, most often AS3356 (Lumen (Level 3)). 6% of its announcements have a valid RPKI ROA; 2 are RPKI-invalid. 73% of its routes reach at least 90% of full-feed peers, and 41 prefixes are also originated by another network.

At a glance

IPv4 prefixes

175

IPv6 prefixes

1

IPv4 addresses

335k

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)USPeer11,05086

Prefixes

All 176

The largest blocks AS203 originates, widest first.

Largest prefixes originated by AS203
PrefixAddressesVisibility
149.21.0.0/1665.5k80/81
170.46.0.0/1665.5k32/81
143.112.0.0/1732.8k80/81
143.112.128.0/1816.4k80/81
206.203.64.0/1816.4k81/81
143.112.192.0/198.2k80/81
143.112.224.0/198.2k79/81
156.42.0.0/198.2k81/81
156.42.32.0/198.2k81/81
156.42.64.0/198.2k81/81

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

  • Valid5.7%10
  • Invalid1.1%2
  • No ROA93.2%164

Propagation

  • Globally propagated90% of full-feed peers or more73.3%129
  • Partially propagated40% to 90%5.1%9
  • Seen by few peersUnder 40%21.6%38

Prefix sizes

IPv4 — 175 prefixes

IPv6 — 1 prefixes

  • /324.3B × /64100.0%1

Recent changes

Announcements that started or stopped since 28th Aug 2026.

27 announced and 2 withdrawn in all; the most recent are shown.

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