CHAPTER 19. FIRST WEBSITE 208
19.5 Troubleshooting Your New Domain
You think you did everything right, but you still cannot get to your website.
What can you do? Here are some troubleshooting steps that can be followed
by yourself or someone helping you.
19.5.1 Caching Causes Time Delay Problems
Caching is an important efficiency “hack” used extensively on the Internet.
By “hack” I mean it is not perfect, but it really helps speed things up.
The main idea behind caching is that things do not change very often. The
picture you retrieved an hour ago is probably identical to the one you would
find if you retrieved it now.
This holds true for domain names and their IP addresses. They rarely
change, so the computers that make up the Internet assume that information
is valid for a day or two, or maybe a week.
You need to be aware that getting things configured properly suffers from
propagation delayproblems. Propagation is the process of sharing infor-
mation from its authoritative source out to the ultimate users.
Domain information is cached so any changes you make will not show up
immediately. In fact, it is hard to tell when they will show up. You need to
be patient.
Specifically, if you have something configured wrong, and you fix it, the rest
of the Internet still may be remembering the way it was before. Your fix
may take time to propagate.
19.5.2 Is the Outside DNS Correct?
First thing to check: Is the world-wide DNS system reporting the correct
IP address for each of your websites?
Do a Google search on “dns lookup” to find websites that will tell you the
current dns information without caching.
http://mxtoolbox.com/DNSLookup.aspxis one example.
http://ping.eu/nslookup/is another example.
https://www.ultratools.com/tools/dnsLookupis another example.