If the default policy is set to accept, then any remote computer outside of the network can establish an FTP connection to the server. Every default policy consists of either of the following actions – accept, reject or drop.Įxample: If no rule is defined for FTP connection to the server on the firewall, the firewall will follow the default policy defined onto it. Due to this, every firewall has a default policy. It is not possible to explicitly define every possible rule on the firewall. Thus, a firewall acts as a barrier between the internal networks and the outside network such as the Internet.

If a firewall receives an ICMP packet, it simply drops the packet and does not allow the packet to enter into the network. Reject: Block the traffic, replying with an “unreachable error”ĭrop: Block/reject the traffic and don’t give any replyįor example, a firewall may have rules configured to allow only HTTP packets. Rules are defined based on the security policy of the organization. A firewall scans all the packets and accordingly accepts, rejects or drops the packet, depending upon the rules configured on it. The main function of the firewall is to screen all the packets entering, leaving and flowing in the network to prevent unauthorized access between two or more computers. A firewall is a network security device placed at the perimeter of the corporate network.

What is a firewall in computer network