I'm reading through some documentation that recommends that, in small networks, all domain controllers should be global catalog servers as well.
To make a domain controller a GC server, follow these steps:
1. Start the Active Directory Sites and Services snap-in.
2. In the console tree, double-click Sites, and then double-click the sitename where
your server resides.
3. Below the Site, double-click Servers, double-click your domain controller, right-click
NTDS Settings, and then click Properties.
4. On the General tab, click to select the Global catalog check box to assign the role of
global catalog to this server if it is not already enabled.