Check a domain expiry date and status from PowerShell with RDAP
A domain stops resolving and the first guess is DNS. Often it is not DNS: the registration expired, the registry put a…
Networking and DNS
Network and DNS troubleshooting on Windows: ipconfig, netstat, route, tracert, nslookup and the PowerShell network cmdlets.
SPF, DKIM and DMARC: why a TXT query finds only SPF
Three DNS records decide whether mail claiming to come from a domain is accepted, and all three are TXT records. That is…
New-NetFirewallRule: why Get-NetFirewallRule shows no ports
New-NetFirewallRule creates an inbound or outbound Windows Firewall rule and attaches it to a policy store, which is the scripted replacement for…
arp command in Windows: reading the ARP cache and finding duplicate IPs
Before a Windows machine can put a packet on the wire for a host on its own subnet, it needs that host's…
route print and route add on Windows: read the routing table and make static routes stick
Every packet that leaves a Windows machine is matched against the local IP routing table before anything touches the wire. The table…
tracert and pathping in Windows: reading hop latency and packet loss
tracert maps the routers a packet passes through on the way to a destination, and pathping takes that same hop list and…
Test-NetConnection in Windows: the PowerShell replacement for ping, telnet and tracert
Test-NetConnection is the built-in PowerShell cmdlet that answers the three questions a sysadmin asks when something on the network stops working: can…
net use in Windows: mapped drives, credentials and error 1219
net use maps a network share to a drive letter, lists what is already mapped, and disconnects it again. That part takes…
netsh command in Windows
netsh (Network Shell) is a command-line scripting utility built into Windows that lets you configure and inspect virtually every aspect of networking…
nmap for Windows: network scanning without installing Linux
Network scanning on Windows usually means installing something or switching to Linux. nmap breaks that assumption - it runs natively on Windows,…