You may wish to keep all of your rewrite rules in a file separate from web.config. This is quite easy to do.
To include rules you may have outside of web.config, you would include them by referencing the filename in the <rules> node’s configSource attribute as shown below:
<system.webServer> <rewrite> <rules configSource="rewriterules.config" /> </rewrite> </system.webServer>
The rewriterules.config file will then contain your rules. It does not require the XML schema declaration and starts directly at the <rules> node:
<rules> <rule name="name of rule"> ... </rule> <rule name="name of rule 2"> ... </rule> </rules>