Network Troubleshooting at the Command Line

nslookup - Lookup information from DNS servers

• Canonical names, IP addresses, cache timers, etc. • Find an ip address - nslookup www.professormesser.com • Find a name - nslookup 8.8.8.8

tracert (Windows) or traceroute (Linux/Unix)

• Determine the route a packet takes to a destination • Takes advantage of ICMP Time to Live Exceeded error message • Not all devices will reply with ICMP Time Exceeded messages

netdom - Manage Active Directory database

• Join a computer to the domain, add a domain account, etc. • Reset domain password • netdom resetpwd /s:server /ud:domain\User /pd:*

net - Windows network commands

• NET USE - Map a network share to a drive letter • net use h: \\<servername>\<sharename> • NET STOP - Stop a service • net stop spooler • NET START - Start a service • net start spooler • NET VIEW - View network resources • net view \\<servername>

ifconfig - Linux/Unix TCP/IP configuration

• ifconfig <interface> - Show TCP/IP details

ipconfig - Windows TCP/IP configuration

• ipconfig /all - Show all TCP/IP details • ipconfig /release - Release the DHCP lease • ipconfig /renew - Renew the DHCP lease • ipconfig /flushdns - Flush the DNS resolver cache

nbtstat - Query NetBIOS over TCP/IP information

• nbtstat -n - List local NetBIOS names • nbtstat -A <ip address> - List remote NetBIOS names • nbtstat -a <device name> - List remote NetBIOS names

netstat - Network statistics

• netstat -a - Show active connections • netstat -b - Show binaries • netstat -n - Do not resolve names

ping - Test reachability

• ping <ip address> - Test reachability to a TCP/IP address • ping -t <ip address> - Ping until stopped with Ctrl-c • ping -a <ip address> - Resolve address to a hostname • ping -n <count> <ip address> - Send a # of echo requests • ping -f <ip address> - Send with Don't Fragment flag set