Due to conflicts among rules, a packet may match more than one rule in a firewall configuration, and the rules that a packet matches may have different decisions. To resolve conflicts, the decision for each packet is the decision of the first (i.e., highest priority) rule that the packet matches. Consequently, the rules in a firewall configuration are order sensitive. To ensure that every packet has at least one matching rule in a firewall configuration, the predicate of the last rule in a firewall configuration is usually a tautology. The last rule of a firewall configuration is usually called the default rule of the firewall.