Mulisite Domain Mapping Redirect type

What type of redirect does the Domain Mapping plugin provide to the search engines, 301 or 302?

I have domainA.com as the primary domain of a multisite subsite set in the Domain Mapping plugin. I then add domainB.com in Domain Mapping for domainA.com as a secondary domain.

What type of redirect does Domain Mapping provide to the search engines/browser for domainB.com?