ABOUT THE SERVICE

Practical network diagnostics from 39D.

The 39D Network Toolbox is a public collection of server-side checks for connectivity, DNS, email authentication, websites, TLS certificates, IP addressing and BGP routing. It is designed to give IT teams, network engineers, website owners and support providers a second observation point when troubleshooting public services.

More than a basic ping page

Alongside ping, traceroute, DNS and WHOIS, the toolbox includes MTR, latency graphs, DNSSEC, SPF, DKIM, DMARC, HTTP security headers, website timing, IPv6, limited TCP port checks, ASN and geolocation data, RIPE RIS route views, a BGP looking glass, RPKI validation, IRR routing consistency and administrator-controlled historical monitoring.

Built around safer public operation

Public diagnostic websites can be abused if they accept arbitrary commands, internal destinations or unrestricted port ranges. This project validates every public target, blocks private and reserved ranges by default, uses fixed command arguments, applies rate limits and restricts the TCP port checker to a configured allow-list.

About 39D

39D provides managed IT support, cyber security and technology services for UK organisations. Related network, internet and VoIP services are available through 39T. Matthew Southgate shares deeper technical work on systems architecture, ISP networks, BGP, MikroTik, IPv6 and resilient infrastructure.