Today we will discuss in detail the Linux iptables firewall and how to secure your server traffic using that awesome firewall.
1 Iptables on CentOS 7
2 How Linux Firewall Works
2.1 Firewall Types
3 iptables Firewall Tables
4 Table Chains
5 Chain Policy
6 Adding iptables Rules
7 Iptables Rules Order
8 List iptables Rules
9 Deleting Rules
10 Replacing Rules
11 Listing Specific Table
12 Iptables User Defined Chain
13 Redirection to a User Defined Chain
14 Setting The Default Policy for Chains
15 Handling ICMP Traffic
15.1 ICMP Message Types
15.2 Connection States
16 Blocking Bad Flags
17 SYN Flooding
17.1 SYN Cookies
18 Drop INVALID State Packets
19 Drop Fragmented Packets
20 Save iptables Rules
Check the complete story
https://likegeeks.com/linux-iptables-firewall-examples/