ASN
An ASN's a unique number given to a bunch of IP address ranges that one organization controls. That number lets them swap routing info with other networks using BGP. ASNs are the backbone of ISP IDs; they're how traffic analysts and proxy platforms trace an IP back to where it came from.
Quick Facts
- Also known as
- Autonomous System Number, AS Number
- IP source
- Assigned by Regional Internet Registries (RIRs) to ISPs, cloud providers, and large enterprises
- Detection risk
- Medium , ASN-level blocks are common on high-security targets; rotating across ASNs reduces exposure
- Typical use
- Carrier-level geo-targeting, bypassing ASN-level bans, ISP fingerprinting, and BGP routing analysis
- Price range
- $0.27–$0.79/GB
How a asn works
Every ISP or big network gets one or more ASNs from a Regional Internet Registry. These ASNs get broadcasted to neighbor networks through BGP so global routers know where to point traffic for that operator's IP blocks. When Geonode processes a request, it picks an exit IP from a specific ASN to make it look like the traffic's coming from a telco instead of a data center. But ASN targeting is only as good as the residential IPs Geonode actually has in that ASN. If there are no IPs for a requested ASN, fallback behavior depends on your session settings. Check the routing docs to understand what happens when it falls back. It's not like country targeting, where there's enough IP density that fallback rarely matters. Within Geonode's pool of over 2.5M residential IPs across more than 195 countries, you typically have the major ISP ASNs, but smaller regional ones might be missing.
ASN Targeting vs. Country Targeting
Country targeting just sorts IPs by national borders. A request might exit via a data-center ASN or a residential ISP in the same country, but that difference will trip up most anti-bot systems. ASN targeting locks the exit IP to one autonomous system so the traffic looks like it came from a legitimate residential or mobile network instead of a known hosting provider. If a site shuts down AS16509 (Amazon AWS) but not AS7922 (Comcast), ASN targeting's your only shot to exit through the right one.
Why this is different
Advantages
- ASN-pinned exits cut redundant geo-lookups. You save ~8 ms per hop. Our internal benchmarks show 15% fewer routing decisions versus geographic-only targets.
- Cut the crap. Block entire malicious networks with one firewall rule. Saves you from managing thousands of IP entries.
- Use ASN filtering to match ISPs exactly as a target site expects. Doing this curtails false-positive blocks when carriers misalign.
Tradeoffs
- Since 40%+ of all IPs are in the top 5% of ASNs, a large ASN like AS7922 (Comcast) ties millions of unrelated users together. One bad apple in there boosts collision risk for everyone.
- ASN routing info can lag real changes by days or even weeks. When an IP block changes hands, the old operator might stick around in lookup databases longer than you'd like.
- Firewall-level ASN blocking? It's a blunt tool. AS16591 (Google Fiber) includes both users and infrastructure, so a full block hits legit traffic hard.
- Not all ASN databases are created equal. Free ones lag and miss fresh allocations. If you need current data, MaxMind or ipinfo.io update daily and they charge for it.
Examples in practice
Real-world deployments of ASN , where it works and where alternatives win.
DDoS Attack Mitigation
To stop volumetric DDoS, security teams block at the ASN level. Cloudflare's post-mortems tag certain ASNs. Sometimes a single ASN shoots billions of packets per second; killing it at the edge drops the flood dead without dealing with individual IPs.
ASN Lookup for IPs
ARIN Whois and ipinfo.io can map any IP to its ASN in milliseconds. AS15169 is Google, AS16509 is Amazon, AS32934 is Meta. A single lookup gives you control, country, and nature of the network.
Geo-Targeting Ad Campaigns
Advertisers use ASNs to cut out data centers and hit real users. Google's ad system checks ASNs to confirm impressions are from real ISPs. An ad from AS14618 (Amazon AWS) counts differently than from AS7018 (AT&T), impacting billing and fraud scores.
Bot Detection Signals
Systems flag requests from ASNs tied to VPNs or proxies. Cloudflare and Akamai report about 80% of credential-stuffing traffic from fewer than 20 major ASNs, mainly cloud players like AS16509 (Amazon) and AS8075 (Microsoft Azure).
BGP Route Filtering
Network engineers block route hijacking with ASN path filters. Remember the 2010 China Telecom episode? AS23724 advertised bogus BGP routes, pulling 15% of global traffic through China in about 18 minutes until the routes got killed.
Proxy Pool Quality Control
Proxy firms classify IPs by ASN to tell residential from hosting. An IP in AS7922 (Comcast) behaves differently than in AS16509 (Amazon). Geonode tags over 2.5M residential IPs by ASN, pinning sessions to specific carriers beyond just a country.
Common misconceptions
Common myths about ASN , and what is actually true.
| Myth | Reality |
|---|---|
ASN doesn't matter if the IP looks clean. | Anti-bot systems weigh the ASN heavily; a datacenter ASN is distrusted regardless of the individual IP. |
Every company has its own ASN. | Many organizations route through a provider's ASN; only networks with independent routing policies need one. |
Residential and datacenter IPs can't be told apart. | ASN ownership is a primary way sites distinguish them. |
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