A computer network has become a necessity for any organization implementing a computer-based information system. hence, keeping the security aspect is important to maintain the network performance so as provide optimum service to its users and to be up against any attacks especially when it isl connected to the internet. this paper intented to give input to computer network administrators who implement IP access control list (ACL) network security system as firewall. it discusses the stengths and vulnerabilities of packing filtering firewall using cisco IP access control list (ACL). the findings of this study will give computer network administrators better understandingon implementing packet filtering firewall with cisco IP ACL and comprehending the potential security holes due to its vulnerabilities.