TCP Header Analyzer — ASN & BGP Route Lookup
ASN, organization, and BGP prefix data — not live TCP header field analysis
How to Use This Tool
- Enter a public IPv4 address, domain, or ASN (AS15169 or 15169).
- ASN-shaped input queries BGPView ASN registry and optional prefixes API.
- IP input maps address to originating ASN and org via geolocation lookup.
- prefixes and prefixCount populate for successful ASN prefix fetches.
- Read note field — IP-only queries return ASN metadata without full prefix tables.
- Use results for ownership attribution — not transport-layer troubleshooting.
About This Tool
True TCP header analysis reads transport-layer fields — source and destination ports, sequence and acknowledgment numbers, window size, flags SYN ACK FIN RST, and options such as MSS and window scaling — from packet captures or firewall logs. VSPIC is transparent: tcp-header-analyzer calls the bgp-route action with IPv4, domain, or ASN input — returning ASN metadata, organization, country, and up to twenty ipv4_prefixes when prefix enumeration succeeds — identical JSON to bgp-route-lookup and tcp-ip-header-analyzer.
There is no live TCP segment dissection, flag parsing, or window size measurement on this page. Use Wireshark or tcpdump on authorized captures for real TCP header analysis. This page establishes routing ownership context when packet captures are unavailable.
Common use cases
- •Measure download and upload speed
- •Test open ports on a home router or server
- •Trace routing paths to diagnose latency
Why use VSPIC for ?
- Honest mapping from IP to ASN and organization ownership.
- ASN queries include sample IPv4 prefix announcements.
- prefixCount shows total prefixes even when display caps at twenty.
- Same bgp-route action as bgp-route-lookup — consistent JSON.
- Useful when logs include IP but not packet captures.
- Free BGPView-backed registry lookup.
Honest disclosure about TCP header analysis
Wireshark displays TCP header breakdown per frame — ports, flags, window, options. Our page does not capture packets and does not return transport-layer fields.
Instead handleBgpRoute runs lookupAsn: IP input yields ASN and org; ASN input queries BGPView for registry metadata and optional IPv4 prefix list.
What bgp-route returns for IP input
IPv4 query returns asn, name, org, country, ip, and prefix fields. Use for abuse attribution when firewall logs show IP without PCAP.
What bgp-route returns for ASN input
AS15169 style input triggers BGPView prefix fetch — up to twenty prefixes and prefixCount. Failed API returns registry-only with note.
Relationship to tcp-ip-header-analyzer
tcp-header-analyzer and tcp-ip-header-analyzer both call action bgp-route with identical JSON — different SEO slugs, same backend and honest limitation disclaimers.
What to use for real TCP analysis
Capture packets on SPAN port or endpoint, inspect in Wireshark. mtr-path-analyzer and traceroute on VSPIC show path hops — complementary to header field parsing.
Relationship to bgp-route-lookup
Prefer bgp-route-lookup for peering documentation SEO; use this page when stakeholders arrive via TCP header search terms.
API action bgp-route
GET /ip-tools/api/extended?action=bgp-route&query=203.0.113.10. Parse asn, org, prefixes, prefixCount.
Authorized use
Registry lookup is passive. Packet capture requires authorization on monitored networks.
Important notes & limitations
- Does not analyze TCP header fields — title is SEO framing, not capability.
- No SYN, ACK, FIN, RST flag inspection or sequence number reading.
- No window size, MSS, or TCP options parsing.
- Prefix API may fail — registry-only fallback with note.
- BGP snapshot is point-in-time — not continuous monitoring.
Frequently Asked Questions
Yes. VSPIC offers this TCP header analyzer at no cost with no account required. Results load in real time.
We do not permanently store your queries on our servers. Some tools run entirely in your browser; others fetch public data for the request only.
Yes. Open the page in any modern phone or tablet browser. Results work on Wi‑Fi and mobile data.
No. It runs bgp-route ASN lookup. Use Wireshark for TCP header dissection.
Yes. Both use action bgp-route with identical JSON — different slug SEO framing.
Yes. action bgp-route with query parameter.
No. This form accepts IP, domain, or ASN query only.
Yes. AS15169 or 15169 returns registry metadata and sample prefixes when available.
bgp-route with the query parameter.
Next step for your check
Continue with bgp route lookup on VSPIC.
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