Have Magento admin on subdomain (admin.mystore.com)

I've asked this on the magento forum but had no response so thought I would try here. 

I am trying to set up my admin url on a subdomain (admin.mystore.com) but it’s not working.

I changed the Custom Admin URL in the admin area to http://admin.mystore.com/ and I have set up the DNS so that admin.mystore.com points to t开发者_JAVA百科he root of the site.

But I can’t login. when I go to the admin URL is just redirects to the homepage.

Anyone know how to set this up correctly?

Thanks

You need to set your default store settings to http://admin.example.com/ and then go into the store website settings, setting the base URL to http://www.example.com/.

You will want to clear your cache settings for good measure.