Can I fake the DNS ip lookup to test my website?
The situation is this: you have a working web site, and you’re about
to move it or make dramatic changes to it. So you make a copy of the web site
at a different ip address, possibly with a different temporary domain name. You
make all your changes and then want to test it out using the correct
URL – the “real” domain name. How can you do that without actually changing the
internet’s DNS entry for your domain?
It’s not hard at all.
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Let’s look at the example in more detail. Say you’re the proud owner of
http://example.com, and it lives on a server at IP address 18.104.22.168. You’re about
to make major changes to it, so you create a new domain, http://test.example.com
on a different server with a different IP address – 22.214.171.124.
After you make your changes, you want (or in come cases you may need)
to test the new server at the new address but use the “correct”, real name
of the site: example.com and not test.example.com.
In other words, you would like to change example.com to point to 126.96.36.199 instead of 188.8.131.52.
Ideally, though, you would not want that to be true for everyone. In fact, you
want that to be true only for you. While you’re testing your new site, you want
the world to continue to only see example.com at the old IP address 184.108.40.206.
Enter the “hosts” file in Windows. This text file contains IP-to-name
mappings that override DNS. In fact, if Windows finds an entry in the DNS file, then
the internet DNS is never even consulted.
The hosts file lives in c:\windows\system32\drivers\etc\hosts (where
“c:\windows” is your Windows directory). It’s just a text file, and each line
that doesn’t begin with a “#” character is of the form:
number space name
So for our example, we would edit this hosts file and add the following
Now, on our machine only “example.com” will reference the new IP address, 220.127.116.11,
instead of whatever DNS has listed.
There are a couple of caveats:
- You’ll need an entry for every and any domain or subdomain you’re testing. So
for example if you needed to test both “example.com” and “www.example.com”, you would
create two entries.
- You must remember to remove the entries from your hosts file after your
testing is complete. Remember, the hosts file overrides DNS, so if the
real IP address for example.com changes again sometime in the future, this machine
will continue to believe it’s at whatever IP address is listed in hosts.
If this approach sounds vaguely familiar, it’s also a technique used
by viruses and spyware. By placing entries into your hosts file, malware writers can
redirect you to their sites or prevent you from accessing
other sites. And that brings us to a final caveat:
- A properly configured anti-spyware or anti-virus program may prevent
you from making changes to your hosts file. It’s safe to temporarily override
these programs settings while you perform your test, but be sure to restore their
real-rime protection when you’re done.