Workshop

Here I Ping Again
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You’ll start off your Internet connection adventure by doing the same kinds of things
This router or firewall is called the choke point because it’s the point at which all traffic could get choked
off if it malfunctions.
you’d normally do internally. The easy part of Internet troubleshooting is that because you more than
likely only have one router or firewall, it’s pretty easy to point the finger at what’s down if you cannot
get to the Internet at all.
If you cannot ping an address right outside your firewall, router, or proxy server, you have a pretty good
idea that your choke point is down. Remember to ping by IP address rather than DNS name—you always
want to make sure that IP connections work before dragging name resolution into the picture. (If IP
connections aren’t working, you can bet your bottom dollar that DNS resolution isn’t working either.)
How do you know what address to ping? Good question! You can ask your provider for the “far side”
address of its router. (No, that’s not a router with snakes, cows, chickens,
You can also use traceroute to trace your path to your favorite WWW address while everything is working
and then write down the second hop that traceroute reports. This is probably the “far side” address of your
ISP’s router.
and a bizarre sense of humor. It’s the router interface farthest from you—the end that isn’t connected to
your system.) You could also simply keep the IP addresses of several reliable Internet hosts handy.
Usually, a ping will resolve a DNS name to an IP address, so just ping a couple of your favorite WWW
addresses and write them down.
My preference tends to be to ping my ISP first and then ping an outside address. If your ISP link is up
but you can’t get to anything else, your link to your ISP could be fine but the ISP’s link to the outside
world may be having problems. Although your ISP probably already knows that it’s having problems
with its link to the outside world, it couldn’t hurt to call and report this.
DNS Problems