Network Troubleshooting at The Command Line

Question 1

PING

Answer 1

• Test reachability
  
  • Determine round trip time
  • Uses Internet Control Message Protocol ( ICMP )
• Primary troubleshooting tool
• Written by Mike Nuuss in 1983

Question 2

IPCONFIG & IFCONFIG

Answer 2

• Most troubleshooting start with your IP address
  
  • Ping your local router / gateway
• Determine TCP/IP & Network Adapter information
  
  • Some additional IP details
• IPCONFIG - Windows TCP/IP configuration
• IFCONFIG - Linux Interface configuration

Question 3

TRACERT

Answer 3

• Determine the route a packet takes to a destination
  
  • Map entire path
  • TRACERT (Windows) or TRACEROUTE (POSIX)

-Takes advantage of Internet Control Message Protocol (ICMP) time to live exceeded error message

• Not all devices will reply with ICMP
  
  • Some firewalls filter ICMP

Question 4

NETSTAT

Answer 4

• Network statistics
  
  • Many different operating systems
• netstat - a
  
  • Show all active connections
• netstat - b
  
  • Show binaries
• netstat - n
  
  • Do not resolve names

Question 5

-NBTSTAT

Answer 5

• NetBIOS over TCP / IP
  
  • Windows NetBIOS traffic using TCP / IP
• NBTSTAT
  
  • Windows utility for querying NetBIOS over TCP / IP information
  • Local & remote devices
• NBTSTAT - n = local NetBIOS names
• NBTSTAT - a = 192.168.1.1 = List by name / IP address
• NBTSTAT - a Server1 - List remote name

Question 6

NET

Answer 6

• Windows network command
  
  • Net stop - Stop a service
  • Net start - Start a service
  • Net use - Map a network share to a drive letter
    
    • net use h: \\
  • Net view - View network resources

Question 7

NETDOM

Answer 7

• Manage Active Directory Database from the command line
  
  • Window 8 or higher
• Join a computer to the domain, add a domain account, remove a domain account
• View domain information

Question 8

NSLOOKUP

Answer 8

• Lookup information from DNS service
  
  • Canonical names , IP addresses , cache timers
• NSLOOKUP
  
  • Both Windows & POSIX based
  • Lookup names & IP addresses
• Find an IP address
• Find name