Basic Firewall Configuration in Cisco Packet Tracer

Prerequisite: Firewall

A firewall is a hardware or software network security device that monitors all incoming and outgoing traffic based on a defined set of security rules, it accepts, rejects, or drops that specific traffic. 

• Accept: Allow traffic.
• Reject: Block traffic but respond with “reachable error”.
• Drop: Block unanswered traffic firewall establishes a barrier between secure internal networks and untrusted external networks, such as the Internet.

Steps to Configure and Verify Firewall in Cisco Packet Tracer:

Step 1: First, open the Cisco packet tracer desktop and select the devices given below:

S.NO	Device	Model Name	Quantity
1.	PC	PC	3
2.	server	PT-Server	1
3.	switch	PT-Switch	1

IP Addressing Table:

S.NO	Device	IPv4 Address	Subnet Mask
1.	Server	1.0.0.1	255.0.0.0
2.	PC0	1.0.0.2	255.0.0.0
3.	PC1	1.0.0.3	255.0.0.0
4.	PC2	1.0.0.4	255.0.0.0

• Then, create a network topology as shown below the image.
• Use an Automatic connecting cable to connect the devices with others.

Step 2: Configure the PCs (hosts) and server with IPv4 address and Subnet Mask according to the IP addressing table given above.

• To assign an IP address in PC0, click on PC0.
• Then, go to desktop and then IP configuration and there you will IPv4 configuration.
• Fill IPv4 address and subnet mask.
• Repeat the same procedure with the server

• Assigning an IP address using the ipconfig command, or we can also assign an IP address with the help of a command.
• Go to the command terminal of the PC.
• Then, type iPConfig <IPv4 address><subnet mask><default gateway>(if needed)

Example: ipconfig 1.0.0.2 255.0.0.0

• Repeat the same procedure with other PCs to configure them thoroughly.

Step 3: Configuring the firewall in a server and blocking packets and allowing web browser.

• Click on server0 then go to the desktop.
• Then click on firewall IPv4.
• Turn on the services.
• First, Deny the ICMP protocol and set remote IP to 0.0.0.0 and Remote wildcard mask to 255.255.255.255.
• Then, allow the IP protocol and set remote IP to 0.0.0.0 and Remote wildcard mask to 255.255.255.255.
• And add them.

Step 4:  Verifying the network by pinging the IP address of any PC.

• We will use the ping command to do so.
• First, click on PC2 then Go to the command prompt.
• Then type ping <IP address of targeted node>.
• We will ping the IP address of the server0.
• As we can see in the below image we are getting no replies which means the packets are blocked.

Check the web browser by entering the IP address in the URL.

• Click on PC2 and go to desktop then web browser.