Computer scientists and network scientists want a speedy, reliable, and nonstop communication. In a communication network, the vulnerability measures the resistance of the network to disruption of operation after the failure of certain stations or communication links. The average lower 2-domination number of a graph G relative to a vertex v is the cardinality of a minimum 2-dominating set in G containing v. Consider the graph G modeling a network. The average lower 2-domination number of G, denoted as gamma(2av)(G), is a new measure of the network vulnerability, given by gamma(2av)(G) = 1/vertical bar V(G)vertical bar Sigma(v is an element of V) (G) gamma(2v)(G). In this paper, above mentioned new parameter is defined and examined, also the average lower 2-domination number of well known graph families are calculated. Then upper and lower bounds are determined and exact formulas are found for the average lower 2-domination number of any graph G.