Implementing Cisco Networking Solutions

Firewalls

Figure 5: Cisco Firewall; source: www.cisco.com

A firewall is a layer 4 device, which essentially is a device that is used to protect the network from any attacks. The firewall basically inspects and filters packets based on predefined rules on the firewall. These rules might be of the following nature:

• Allow TCP outgoing connections only
• Rate limit TCP connection requests to a specific rate
• Block all TCP traffic on a specific port
• Block all UDP traffic on a specific port

Organizations generally use IP addresses that are not routable on the public internet. This prevents the users within the organization from accessing public internet ...