By Paul Tero CHAPTER 8The -q 1 option on Mac and Linux tells the command to try each router
only once. The -n tells it not to bother looking up the human-readable
name for each router, which makes the command much slower. This
option is -d on Windows, so use tracert -d 1.2.3.4.
Each step above is known as a hop in networking jargon. The first hop
is the broadband router. It is probably configured not to provide any infor-
mation about itself, so traceroute just shows an asterisk. The second hop
takes it outside the local network to the other side of the broadband router.
At each subsequent hop sits another router, probably with many
network interfaces and many IP addresses. Each router has a routing table
like the one above. Its table contains rules like: if the destination starts
with 0 to 91, then send the packet down interface eth1 (the Use Iface
column); if it starts with 92 to 128 , use eth2.
This example goes 14 hops before reaching a dead end, either because
the IP address is blocked or not in use.
That is about as far as numbers alone can take us. Hopefully you’ve
established that civilization is still going at least a couple networking
hops beyond your front door. You’ve also learned how to use the useful
networking commands ifconfig, ping and traceroute. To explore further,
you’ll need DNS.
The Domain Name System
Smashing Magazine could have gone with http://80.72.139.101 as its main
website address rather than http://www.smashingmagazine.com. It would
have had two advantages: it would have used less space on business cards;
and it would still have worked when DNS was down. However, Smashing’s
marketing people may have objected, and their customer base would have
been limited to people with extremely good memories.
The domain name system makes the Internet more human-friendly
by translating between domain names like http://www.smashingmagazine.com
and IP addresses like 80.72.139.101. DNS is a big hierarchical distributed