AS213761 · Federal State Budgetary Educational Institution of Higher Education Lomonosov Moscow State

An autonomous system is the unit networks use to route traffic between each other. A BGP ASN lookup for AS213761 shows how Federal State Budgetary Educational Institution of Higher Education Lomonosov Moscow State is registered, which IP prefixes are associated with the network, and which peers or upstreams appear in the available routing data.

The announced prefixes table helps you find IP prefixes by ASN and inspect CIDR blocks tied to the organization. The peering section shows neighboring networks it exchanges traffic with — upstreams sell it transit, while peers swap traffic directly. Together they describe both what this network reaches and how it connects.

Use ASN profiles for network owner lookup, incident triage, IP range review and provider research. Treat the data as routing context, not live outage monitoring; BGP changes can move faster than public lookup datasets.

Accepted input formats

AS15169, as15169 and 15169 all open the same profile — everything except the digits is ignored. Try the examples above: AS15169 (Google), AS13335 (Cloudflare) and AS36459 (GitHub).

Reading a profile

The raw response for a hypothetical network using the documentation number AS64500 might look like this:

{
  "asn": "AS64500",
  "handle": "EXAMPLE-NET",
  "org": "Example Networks Ltd",
  "country": "NL",
  "rir": "RIPE NCC",
  "registered": "2015-06-01",
  "ipv4_prefixes": 12,
  "ipv6_prefixes": 3,
  "addresses_v4": 6144
}

Twelve IPv4 blocks totalling 6,144 addresses could be four /22 blocks (1,024 addresses each) plus eight /24 blocks (256 each) — a small hosting company or regional ISP. Three IPv6 blocks show that the network also routes IPv6. A real lookup for AS64500 returns No results, because documentation numbers are never used on the internet.

Numbers that return No results

Documentation ASNs (64496–64511), private ASNs (64512–65534 and 4200000000–4294967294) and AS0 are not used on the public internet, so they show the not-found message.

• Handle, Organization, Country, RIR, Registered — from CAIDA's AS-to-Organization dataset. Country is the organization's registration country, not where its routers are; when CAIDA has no country, the tool geolocates the first listed prefix instead. Registered is the date on CAIDA's record, which can reflect a later record update rather than the original assignment.
• Type badge and website — the network type (for example ISP, Content or NSP) and website the operator published in PeeringDB. Unknown means the network has no PeeringDB entry.
• IPv4 prefixes, IPv6 prefixes, IPv4 addresses — counts of the address blocks the MaxMind GeoLite2 ASN database maps to this AS; the address total adds up the size of every IPv4 block. The database can split or merge blocks differently from BGP announcements, so treat the counts as a size estimate.
• Announced prefixes — a sample of up to 20 IPv4 and 8 IPv6 blocks, lowest addresses first; the badge shows how many are listed. IPv6 rows show — instead of an address count. Click a prefix to open its first address in IP Lookup.
• Peering & transit and Observed peers — business relationships from CAIDA's AS-relationship dataset, which infers them from public BGP paths. The list shows up to 12 upstreams (transit providers), 14 peers and 12 downstream customers; Observed peers is the total number of neighbours of all three kinds. The diagram plots the same sample around this AS.

• Attributing traffic. Find the ASN of an address from your logs with IP Lookup, then check here whether the network is an ISP, a content network or a transit provider.
• Starting a network-level block or allow-list. The prefix table shows which ranges belong to the AS, but it is only a sample — pull the complete prefix list from routing data before writing firewall rules.
• Comparing hosting or transit providers. Prefix counts, IPv4 address totals, IPv6 presence and upstream providers give a quick sense of a network's size and how it connects.
• Incident triage. When a range is unreachable, the upstream list shows which transit providers carry that network's traffic.

New to autonomous systems? Read What is an ASN? for how ASNs, BGP and prefixes fit together.

No results for an ASN that exists

A profile is only available when the GeoLite2 ASN database maps at least one address block to the number. Registered ASNs that announce nothing — newly assigned, decommissioned or used only for private interconnects — show the not-found message.

Handle, RIR or Registered is blank

The number is missing from the CAIDA organization dataset loaded by the tool. Prefix counts still come from MaxMind, so the profile is shown with the organization name MaxMind has.

An address I expected is not in the prefix table

The table is a sample of the lowest blocks. The address may also be routed by a different AS — for example, a company that uses a cloud provider's address space. Look the address up directly to see which ASN covers it.

Counts differ from another BGP tool

Route collectors count announced prefixes as seen in BGP, while this page counts database blocks. Both are valid views of network size but rarely match exactly.

• All sources are periodic dataset snapshots, not a live BGP feed. Relationships are inferred by CAIDA and can miss private peering.
• Abuse contacts are not shown, because none of the loaded datasets publishes them. Query the responsible regional internet registry's RDAP or WHOIS service for the abuse contact of a network.
• The tool does not validate RPKI route origins, detect route hijacks or leaks, read IRR route objects, or check blacklists and reputation.