Jun 03

Creating Dynamic Subdomains using ISAPI_Rewrite

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Using ISAPI_Rewrite

Whoa! That’s a lot of steps to create all the subdomains I want. Is there an easier way? Well there is an alternative way. Let’s get started first then we’ll run the comparisons.

Setup DNS Server

Add the following entry into your DNS server and change the domain and IP address accordingly.

*.example.com IN A 1.2.3.4

Setup the Web Server

We are assuming that you already have a web site created for your main site: www.example.com. So let’s just double check to make sure it will be able to accept all variations of the subdomains.

  • Open IIS Management Console and select your web site.
  • Right click on it and select Properties.
  • Click on Web Site tab.
  • Click on Advanced button.
  • Make sure there is one entry under the Multiple identities for this Web Site with Host Header Name field blank. This entry will intercept all requests that comes to this IP address.
  • Make sure the IP address is only used by this web site.

Setup httpd.ini for ISAPI_Rewrite

Add the following code to your httpd.ini in the web root. Make sure they are in the correct order.

# Convert http://example.com to http://www.example.com/
RewriteCond Host: ^example.com
RewriteRule (.*) http\://www\.example.com$1 [I,RP]

# Assuming we have limited number of shared folders.
# We will execute them accordingly regardless of the subdomain.
# Example: http://sub1.example.com/img/logo.jpg -> /img/logo.jpg
# Example: http://www.example.com/img/logo.jpg -> /img/logo.jpg
RewriteRule (/css/.*) $1 [I,O,L]
RewriteRule (/js/.*) $1 [I,O,L]
RewriteRule (/img/.*) $1 [I,O,L]

#Redirect all other subdirectories not matching
#to the list above as subdomains
#example: www.example.com\sub1 -> sub1.example.com
RewriteCond Host: www\.highspeed\.com
RewriteRule /(\w*)/(.*) http\://$1\.example\.com$2 [I,RP]

# If the web site starts with www then point the file to the root folder
# If you specifically created a folder /www/ then you can comment out this section.
RewriteCond Host: (?:www\.)example.com
RewriteRule (.*) $1 [I,O,L]

# Any web site starts other than www will be re-mapped to /<subdomain>/
# Example: http://sub1.example.com/default.asp -> /sub1/default.asp
# Note: if the folder does not exists, then the user will get a 404 error automatically.
RewriteCond Host: (.*)\.example.com
RewriteRule (.*) /$1$2 [I,O,L]

#Fix missing slash char on folders
#This has to be at the end because if invalid dir exists,
#we should show 404 first
RewriteCond Host: (.*)
RewriteRule ([^.?]+[^.?/]) http\://$1$2/ [I,RP]