For new sites, use XRouting instead. That has the same features, and then some.
ContextRouter is a simple plug-and-play plugin allowing you to use different contexts, and, based on the http_host context settings you need to set anyway, it routes your front-end requests as required.
Install the plugin and make sure your contexts have a http_host variable set. If it doesn't seem to route properly, try clearing the cache to update the context - http_host caching.