What is a Firewall
Firewalls are used to protect a network's data and resources from outside access and threats. A Firewall is used as a barrier between a internal network of an organization and another network (may be public internet or another network of the same organization).
Since the primary function of a Firewall is to protect a network's data and resources from outside threats, they are usually placed at the end point of a network.
A firewall can be a dedicated Hardware device, or Software running in a computer.
Firewalls can be configured with "rules". Firewall rules can be used to allow/deny network traffic from/to the network. These rules can be based on Source/Destination network, Source/Destination IP Address, Source/Destination TCP/UDP port numbers, Protocols, Applications etc.
Following image shows a Cisco ASA 5520 firewall device
Chapter 1 :- Introduction to Computer Networking
Chapter 2 :- What is a Computer Network
Chapter 3 :- Why we need computer networks
Chapter 4 :- Client Operating Systems
Chapter 5 :- Common Network Application Software
Chapter 6 :- LAN and WAN
Chapter 7 :- CAN and MAN
Chapter 8 :- Peer-to-Peer networks and Client-Server networks
Chapter 9 :- Centralized and Distributed Computer Networks
Chapter 10 :- Internetworks, Internet, Intranet and Extranet
Chapter 11 :- What is a Network Protocol
Chapter 12 :- Difference between Proprietary and Standard Protocols
Chapter 13 :- What are RFCs
Chapter 14 :- Organizations which control Internet
Chapter 15 :- Bus Topology
Chapter 16 :- Star Topology
Chapter 17 :- Mesh, Ring and Hybrid Topologies
Chapter 18 :- Network Infrastructure Devices and Icons
Chapter 19 :- Network Hub
Chapter 20 :- Network Bridge
Chapter 21 :- What is a Router
Chapter 21 :- What is a Firewall
Chapter 22 :- Office Networks
Chapter 23 :- Hub-and-spoke WAN topology
Chapter 24 :- Partial-Mesh WAN topology
Chapter 25 :- Full-mesh Site-to-site WAN topology
Chapter 26 :- What is NIC
Chapter 27 :- Common Network Cable types
Chapter 28 :- Difference between Baseband and Broadband
Chapter 29 :- CSMA/CD, CSMA/CA and Token Passing
Chapter 30 :- LAN Technologies Ethernet
Chapter 31 :- Ethernet Media Standards
Chapter 32 :- What is Token Ring
Chapter 33 :- What is FDDI
Chapter 34 :- IEEE 802 Standards
Networking Interview Questions :- 1
Networking Interview Questions :- 2
Networking Interview Questions :- 3
Networking Interview Questions :- 4
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