SharePoint 2010 Central Administration on port 80

Hi,

I have created CA using powershell on port 80. URL for CA is "http//host_name/". Then I used Alternate Access Mappings to change "http//host_name/" tohttp://ca.company.com.  But still access only works for http//host_name.

How to configure correctly to have CA URL http://ca.company.com and have only one site "SharePoint Central Administration v4" in IIS without host header in bindings. We have this configuration on live, but I can not repeat the same on dev.

Extending the site also is not the correct way because it creates additional site in IIS.

Is it possible to add custom URL like "http://ca.company.com" to New-SPCentralAdministration then cmdlet runs or smth?

Thanks