Part A:-
=>We first configured the firewall for the pre-conditions mentioned as follows:
a)For outgoing traffic (from 10.20.111.0/24 to 10.10.111.0/24) - your internal machine should be able to communicate with the external network and the external machines without restrictions iptables –A OUTPUT –s 10.20.111.0/24 –d 10.10.111.0/24 –j ACCEPT -m state --state NEW,ESTABLISHED,RELATED

b)For incoming traffic (from the 10.10.111.0/24 to the 10.20.111.0/24) - all incoming connection requests should be rejected with the following exceptions. iptables –A INPUT –s 10.10.111.0/24 –d 10.20.111.0/24 –j REJECT -m state --state NEW,ESTABLISHED,RELATED. iptables –A FORWARD –s 10.10.111.0/24 –d 10.20.111.0/24 –j REJECT -m state --state NEW,ESTABLISHED,RELATED. …show more content…
=> iptables is a generic table structure for the definitions of ruleset.
=> Each ruleset consists of classifiers (iptables matches) and one connected action (iptables target/jump).
=>The iptables firewall operates by comparing network traffic against a set of rules. The rules define the characteristics that a packet must have to match the rule, and the action that should be taken for matching packets
=>When the defined pattern matches, the action that takes place is called a target. A target can be a final policy decision for the packet, such as accept, or drop. It can also be move the packet to a different chain for processing, or simply log the encounter.
=>Hence using firewall we can configure rules for our server, depending on our needs.

2) What is the difference between input, output and forward chains?
=>There are three type of chain in iptables viz input, output and forward chains.
INPUT: This chain handles all packets that are addressed to the firewall.
OUTPUT: This chain contains rules for packets destined to the firewall.
FORWARD: This chain is used to deal with packets passing the firewall. This chain is basically a way to configure the server to route requests to other …show more content…
=>Reject will drop the packet notifying the sender that host is unreachable.
=>Deny drop the packet but it will drop silently without notifying the sender. =>Accept allows the packet to pass through or will receive the packet.

4) Do some research and find some three alternative network based firewalls. List and describe the pros and cons of each when compared to iptables. The alternative can be commercial, open source or even a stand-alone appliance.
Tixati-
=>It is type of network based firewall having some improvement over simple