A router is a device that links multiple networks and directs traffic between networks. Each network linked by routers has its own unique identifier called the “network number” or “network address.”
The role of a firewall is to provide a barrier between an organization’s network and a public network, such as the Internet. Its job is to prevent unauthorized access into the organization’s private network. To do this, the firewall examines incoming packets and determines whether they should be allowed to enter based on a set of rules defined by the network administrator.
A firewall is the best device to deploy to protect your private network from a public untrusted network. Firewalls are used to control traffic entering and leaving your trusted network environment. Firewalls can manage traffic based on source or destination IP address, port number, service protocol, application or service type, user account, and even traffic content.
Routers offer some packet-based access control, but not as extensive as that of a full-fledged firewall. Hubs and gateways are not sufficient for managing the interface between a trusted and an untrusted network.
Firewalls prevent unauthorized users from accessing private networks connected to the internet. You should never allow public access to your DHCP server. A proxy server caches web pages. A NAT router or ICS translates Web addresses to private IP addresses. A proxy server and NAT software might be implemented on the same device as your firewall, but they are different concepts.
Packet Internet Groper
A firewall allows you to filter unwanted traffic from the Internet to your network. Packet Internet Groper is better known by its acronym, PING, a TCP/IP command. A proxy server caches web pages. ICS allows you to connect a small network to the Internet through a single connection.