16 - More Pinging and Intro to DNS
- Troubleshooting our malfunctioning network
	- We have confirmed that your LAN is not the problem
	- time to look to the outside…
	- How?
		- PING STUFF!
	- First question. Can I reach my ISP
		- Look in the router for the default Route, which is somewhere in your ISP
	- If this works, your traffic is getting all the way through your ISP
		- next, ping something somewhere else, outside your LAN and ISP
			- Use this one: the typicalmacuser.com <http://typicalmacuser.com/> IP addresss
				- 68.178.254.63
			- if this works, nothing is actually wrong with your internet connection in the sense that your packets are getting to where they need to go
- Something else must be wrong
	- Odds are, it is DNS
- the Internet works off of IP addresses
	- but we humans don't use IP addresses
		- we use URLs, like bartb.ie <http://bartb.ie/>
- The Domain Name Service, or DNS, translates these human readable URLs to IP addresses computers can use to talk
- If your DNS isn't working, you won't be able to do anything with it
- To test this, you can do a direct lookup using the 'host' command
	- host anyurl.com
	- host typicalmacuser.com
	- if it is working, it'll tell you the IP address of the URL you put in
- By this stage, odds are you have found out what the problem is
	- If it doesn't work, check in your router to make sure DNS is set up properly, then call your ISP to make sure their DNS server is working
- One thing you might consider doing is using different DNS servers
	- DNS servers are frequently the targets of attacks, and ISP DNS servers aren't always great
		- . A company called OpenDNS, from opendns.com <http://opendns.com/> offers free use of their DNS servers, which are held to be very secure, very reliable, and faster than your run of the mill ISP DNS server.
			- to Use their DNS servers, simply put the following IP addresses as your DNS servers on either your router or computer. for more detailed instructions and to see some of the other cool features they offer, check out their website
				- primary: 208.67.222.222
				- secondary: 208.67.220.220
		- It is generally good to commit these IP addresses to memory, since changing your DNS servers to OpenDNS is another good troubleshooting step to check
		- If you want to learn more about OpenDNS, George Starcher did an excellent three part screencast over at typicalmacuser.com <http://typicalmacuser.com/> about OpenDNS. go check it out
			- Part 1: TMUPS-014 OpenDNS Turorial Part 1 <http://typicalmacuser.com/wordpress/2008/03/19/tmups-014-opendns-turorial-part-1/>
			- Part 2: TMUPS-015 OpenDNS Turorial Part 2 <http://typicalmacuser.com/wordpress/2008/03/20/tmups-015-opendns-turorial-part-2/>
			- Part 3: TMUPS-016 OpenDNS Tutorial Part 3 <http://typicalmacuser.com/wordpress/2008/03/21/tmups-016-opendns-turorial-part-3/>
- Next Podcast completely devoted to DNS…
- but for now, brief detour to an almost completely useless for most people, but cool and interesting, command
	- traceroute
		- similar to ping, but instead of endpoint to endpoint, it shows you the location of each hop the packet takes to routers on the way to the entire destination
			- also shows you the speed in milliseconds between hops
		- unfortunately, not all routers return IGMP packets, which are the packets that traceroute uses
		- traceroute anyurl.com
		- traceroute bartb.ie
- Bart Busschots
	- bartb.ie <http://bartb.ie/>
	- impodcast.tv <http://impodcast.tv/>
	- podfeet.com <http://podfeet.com/>