Router firewall
Routers usually support one or more of the firewall features discussed previously. Router firewalls are usually available by default on low-end routers designed for Internet connections; they provide basic firewall features for blocking and allowing specific IP addresses and port numbers and use NAT to hide interior IP addresses.
High-end routers can be configured to tighten up access by barring more obvious intrusions, such as pings, and by implementing other IP address and port restrictions through the use of ACLs. Additional firewall features may be available that provide stateful packet filtering in some routers. In high-end routers, the firewall capability is similar to that of a hardware firewall device at a lower cost but also lower throughput.