Network · AS3128

AS3128 University of Wisconsin System

AS3128 (University of Wisconsin System) looks like an internet service provider, so its addresses are mostly real home, business or mobile connections.

Network check ASN

AS3128

OwnerUniversity of Wisconsin System
KindInternet service provider
Servers, not peopleno
IPv4 addresses655,616
IPv4 ranges11
IPv6 ranges1

Risk score0

Nothing suspicious found.

Largest IPv4 ranges

144.13.0.0/16
143.236.0.0/16
143.235.0.0/16
143.200.0.0/16
141.233.0.0/16
139.225.0.0/16
138.49.0.0/16
137.81.0.0/16
137.104.0.0/16
131.210.0.0/16
192.35.81.0/24

Ranges and owner from DB-IP (CC BY 4.0), updated 2026-10-21.

Check an IP address →

Detect it in code

Spot AS3128 traffic at signup.

Send the visitor's IP. The response includes the ASN, the owner and flags.hosting.

curl https://veqen-app.com/v1/ip/check \
  -H "Authorization: Bearer $VEQEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"ip": "203.0.113.7"}'

import os, requests

r = requests.post(
    "https://veqen-app.com/v1/ip/check",
    headers={"Authorization": f"Bearer {os.environ['VEQEN_API_KEY']}"},
    json={"ip": "203.0.113.7"},
    timeout=10,
)
result = r.json()
print(result["risk"]["verdict"], result["risk"]["reasons"])

const res = await fetch("https://veqen-app.com/v1/ip/check", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.VEQEN_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({"ip": "203.0.113.7"}),
});
const result = await res.json();
console.log(result.risk.verdict, result.risk.reasons);

Questions

About AS3128

Is AS3128 a datacenter or VPN network?

AS3128 (University of Wisconsin System) looks like an internet service provider, so its addresses are mostly real home, business or mobile connections.

Who owns AS3128?

AS3128 is registered to University of Wisconsin System. It announces about 655,616 IPv4 addresses.

How do I detect traffic from AS3128?

Call the Veqen IP check with the visitor's address. The response includes the ASN, the owner and whether the network is a datacenter, VPN network, relay or ISP.