Netdiag helps isolate networking and connectivity problems by performing a series of tests to determine the state of your network client and whether it is functional. These tests and the key network status information they expose give admins a more direct means of identifying and isolating network problems.
Netdiag performs its tests by examining .dll files, output from other tools, and the system registry to find potential problem spots. It checks to see which network services or functions are enabled and then runs the network configuration tests. If a computer is not running any of those network services, the test is skipped.
NDIS – Network Adapter Status
ipconfig – checks the Wins,DNS,DHCP,Gateways and pings
netstat – TCP/IP statistics
Route – Route test
Also, tests the DNS registration, Domain membership, Wins, NetBt, Winsocks and others. Although, there is no need for any switches, there are some that comes handy when required.
The switches are
/q – Lists only errors. Quiet output
/v – Verbose output. Detailed output
/l – logs to netrdiag.log file in default folder
/debug – Enhanced verbose output
/d:<Domain> – Finds the Domain Controllers in the domain
/fix – Fix DNS problems
/DCAccountEnum – Enumerate
DC /test:<test name> – Only specific test than all
/skip<test name> – Skip specific test
Any error maked as FATAL needs immediate fixing whereas a WARNING needs fixing but not very critical.