ccna 300-125

ccna 300-125.A unique transport point between networks (all traffic passes through the firewall).Enforcement of access control policies.In 1988, DEC created the first network firewall in the form of packet filtering. These early firewalls examined packets to see if they matched a rule and thus chose whether to forward or discard them. This type of packet filtering firewall, also known as stateless filtering, does not consider whether a packet is part of an already existing data flow. Each packet is filtered individually based on a specific parameter value in the packet header, which is similar to the filtering mechanism of an ACL.The first stateful firewall was developed by AT&T Bell Labs in 1989. A stateful firewall first stores information about the data streams traversing the firewall into the firewall and then filters the packets based on this information. It determines whether packets belong to an already existing data stream. It applies mainly static rules (as in packet filtering firewalls) and dynamic rules created in real time to define these active flows. Stateful firewalls help mitigate such DoS attacks, i.e., attacks launched using active connections that traverse the firewall device.Initially, firewalls were not separate devices, but rather routers or servers with software installed that provided firewall functionality. Over time, many companies developed standalone firewalls. Dedicated firewall devices freed routers and switches from having to deal with memory-intensive and processor-intensive packet filtering. For companies that do not need to use a dedicated firewall, modern routers, such as Integrated Services Firewall (ISR), can also be used as advanced stateful firewalls.4.2.1.2 Pros and Cons of FirewallsUsing a firewall in a network has the following benefits:Prevents sensitive hosts and applications from being exposed to untrusted users;Cleanses protocol traffic from exposing protocol vulnerabilities;Keeps servers and clients away from malicious data;Makes the implementation of security policies simpler, more scalable, and more robust when the firewall is properly configured;Reduces most network access control efforts to just a few points, thereby reducing the complexity of security management.Firewalls also have some limitations: They can cause serious problems (such as a single point of failure) if not configured properly.102 Chapter 4 Implementing Firewall TechnologiesData from many applications cannot pass safely through the firewall; Users may actively seek ways to bypass the firewall to receive blocked information, exposing the network to the risk of potential attacks; Network performance may degrade; and Unauthorized traffic may pass through the firewall via tunnels or hidden within legitimate traffic. It is important to focus on understanding the different types of firewalls and their specific functions so that the correct firewall can be selected for use in different situations.