15-Discovering Your Network
- When troubleshooting a network…
    - 1. ifconfig
        - basic network setup
        - make sure you even have a connection
        - routed traffic vs LAN traffic
    - 2. Make sure you have a clean connection to your router
        - does your mac know which machine the router is?
- netstat
    - extremely powerful
    - netstat -rn 
        - -r outputs routing tables
        - Normally netstat does DNS lookups to change the IP addresses
          into URLs
            - we dont want that, because all the IP addresses we are
              looking at are LAN IP addresses
            - -n leaves them as IP addresses
    - Output:
        - Routing Tables 
            - Internet (refers to IPv4)
                - columns:
                    - destination
                    - gateway
                    - Flags
                    - Refs
                    - Use
                    - Netif
                    - Expire
            - Internet6 (refers to IPv6)
                - Columns
                    - Destination
                    - gateway
                    - Flags
                    - Netif
                    - Expire
                - Just ignore this part
    - Look at the Internet: Default and Gateway Columns
        - under Destination, look for Row that starts with default
            - note the IP address for that row under gateway
            - that is the IP address of your router's default gateway
        - If you have more than one Network interface at a time
          (ethernet, wifi, etc)
            - look under the Netif column to see which one
    - Now we know the IP address of what your mac thinks is the default
      gateway
- ping
    - sends out an ICMP packet to a specified target, and requests a
      reply
    - ping some IP address
        - or a URL
    - rows of data should start flowing down the screen
        - will ping infinitely until told to stop
        - they are listed as they are received
            - not when they are sent
    - to kill: CTRL+C
    - Shows two summary lines
        - # packets transmitted, # packets received, % Packet loss
            - on your local network, you should NEVER have packet loss
                - if you do, you have hardware problems, like weak wifi
                  signal, or a frayed Ethernet cable
        - round-trip min/avg/max/stddev = #/#/#/# ms
    - If the Ping works, then the problem exists between the Router and
      the Internet
-
- Bart Busschots
    - bartb.ie <http://bartb.ie/>
    - impodcast.tv <http://impodcast.tv/>
    - podfeet.com <http://podfeet.com/>