Final answer:
In network security rules, the absence of specified interfaces implies a universal rule that applies to traffic from any source to any destination, indicating no restrictions based on interfaces for traffic flow.
Step-by-step explanation:
If 'interface' specifications are not present in a network command or firewall rule, it typically means that the rule applies to traffic going from any interface to any interface; in other words, from any source to any destination. This concept is a fundamental part of network security rules and configurations, which are used to control the flow of data across various parts of a network. An absence of specified interfaces in the rule suggests that no restrictions are based on the origin or target interfaces of the network traffic, making the rule universal within the context it is applied.