Why a phone shows different MAC addresses
Read the U/L bit, understand per-network privacy addresses, and interpret a vendor lookup carefully.
Guides
Networking guides
Use the tools with a clearer understanding of what their results establish.
These guides explain the underlying mechanisms and the limits of a result. They link to the primary standards and to the tools that can help you work through an example. Guides about remote checks describe the method; those checks are planned and are not deployed yet.
Annotate a device inventory
Turn an ARP table or DHCP export into an assignment-aware CSV while keeping unknown and private addresses honest.
Plan IPv4 and IPv6 subnets
Work through prefix lengths, VLSM, aggregation and the boundary mistakes that cause overlapping ranges.
Troubleshoot a DNS answer
Separate authoritative data from cached answers, and distinguish NXDOMAIN from NODATA.
Read an email authentication result
Understand SPF, DKIM, DMARC alignment and MTA-STS before changing published records.
Read a TLS scan report
Interpret protocol support, certificates, evidence and incomplete scan coverage.