Packet-filtering firewall/stateless firewall

This type of firewall is nothing but routers that connect the internal network to the external network. Packet-filtering firewalls work on the network layer and the transport layer of the OSI model. Routers configured with an ACL are packet-filtering firewalls. An ACL can be defined based on the IP address, protocols, and packet attributes (IP header), as shown in the following diagram. If a packet does not meet the configured policies and rules, the packet is discarded and the routers will create a log: