How Do You Build An SEO Shield With A Domain That Has Multiple Subdomains?

In episode 302 of our weekly Hump Day Hangouts, one viewer asked how to build an SEO shield with a domain that has multiple subdomains.
The exact question was:
2) If you have a domain that has subdomains, each subdomain has different purpose of a niche (not for leadgen, niches like dogs, cats, sports, etc). How should it have be built with seo shield? shield to the top domain and shield to each subdomain?
