COMPUTER NETWORKING

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NETWORK SECURITY

FIREWALLS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
iptables is used to configure, maintain and inspect IPv4 packet filtering rule tables in the Linux kernel. Several different tables can be defined. Each table contains a number of internal chains and can also contain user-defined chains. If the network technician wanted to deny access to port 443 of a certain Linux server, the command used in this case is represented in the alternative:
A
iptables-R INPUT-h tcp ____ dport 443-d REJECT
B
iptables-A INPUT-p tcp ____ dport 443-j DROP
C
iptables-L INPUT-d tcp ____ dport 443-j ACCEPT
D
iptables-I INPUT-s tcp ____ dport 443-d REJECT
Explanation: 

Detailed explanation-1: -Question 1. What Is Iptables ? Answer : iptables is a user space application program that allows a system administrator to configure the tables provided by the Linux kernel firewall (implemented as different Netfilter modules) and the chains and rules it stores.

Detailed explanation-2: -The masquerade target is only valid in the nat table. Usually, we apply this to dynamic IPs. For static IPs, iptables provide another target named SNAT. The forward chain in the filter table enables packet forwarding within a network.

Detailed explanation-3: -The 3 main tables in iptables are the Filter, NAT, and Mangle tables. The Filter Table is used to control the flow of packets in and out of a system. The NAT Table is used to redirect connections to other interfaces on the network. The Mangle Table is used to modify packet headers.

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