1.2 - The Windows Network Command Line

Question 1

CMD - ipconfig

Answer 1

• Most of your troubleshooting starts with your IP address
  – Ping your local router/gateway
• Determine TCP/IP and network adapter information
  – And some additional IP details
• View additional configuration details
  – DNS servers, DHCP server, etc.

Question 2

CMD - ping

Answer 2

• Test reachability
  – Determine round-trip time
  – Uses Internet Control Message Protocol (ICMP)
• One of your primary troubleshooting tools
  – Can you ping the host?

Question 3

CMD - netstat

Answer 3

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

Question 4

CMD - nslookup

Answer 4

• Lookup information from DNS servers
  – Canonical names, IP addresses, cache timers, etc.
• Lookup names and IP addresses
  – Many different options

Question 5

CMD - net

Answer 5

Question 6

CMD - tracert

Answer 6

• Determine the route a packet takes to a destination
  – Map the entire path
• Takes advantage of ICMP Time to Live Exceeded
  message
  – The time in TTL refers to hops, not
  seconds or minutes
  – TTL=1 is the first router, TTL=2 is
  the second router, etc.
• Not all devices will reply with ICMP Time Exceeded
  – Some firewalls filter ICMP
  – ICMP is low-priority for many devices

Question 7

Flavors of traceroute

Answer 7

• Not all traceroutes are the same
  – Minor differences in the transmitted payload
• Windows commonly sends ICMP echo requests
  – Receives ICMP time exceeded messages
  – And an ICMP echo reply from the
  final/destination device
  – Unfortunately, outgoing ICMP is commonly filtered
• Some operating systems allow you to specify the
  protocol Linux, Unix, macOS, etc.
• IOS devices send UDP datagrams over port 33434
  – The port number can be changed with extended options
  – The mechanics of traceroute

Question 8

CMD - pathping

Answer 8

• Combine ping and traceroute
  – Included with Windows NT and later
• First phase runs a traceroute
  – Build a map
• Second phase
  – Measure round trip time and packet loss at each hop