The Kerberos protocol either searches the configuration file to determine realm trust or by default looks for trust relationships within the realm hierarchy. Using Trusted realms in network authentication service allows you to bypass this process and creates a shortcut for authentication. Realm trust can be used in networks where realms are in different domains. For example, if a company has one realm at NY.myco.com and another at LA.myco.com, then you can establish trust between these two realms. If two realms trust each other their associated KDCs must share a key. Before creating a shortcut, you must set up the KDCs to trust each other.