A packet filtering router is a device that uses packet filtering techniques to control incoming and outgoing network traffic based on predetermined security rules.
Packet filtering is a basic and efficient technique for controlling network traffic, but it has some limitations. It is relatively simple to bypass and can be difficult to manage when there are many rules in place.
Packet filtering routers typically have a set of rules, also known as a “access policy,” that specifies which traffic is allowed and which is denied, based on various criteria such as the source and destination IP addresses, ports, and protocols.
These rules are applied to incoming and outgoing packets, and packets that do not meet the specified criteria are dropped or rejected by the router. By Default, all packets are rejected as per implicit deny all configuration.
Packet filtering routers are commonly used in small and medium-sized networks to provide basic security and control over network traffic.
They can be configured to allow or deny specific types of traffic, such as web traffic, email, or remote desktop connections based on port and protocols only and can be used to protect networks from various types of unauthorized access.
While packet filtering routers are effective at controlling network traffic, they have some limitations.
They do not provide protection against more advanced threats, such as encrypted traffic or application-level attacks, and may not be sufficient for larger or more complex networks.
In these cases, more advanced firewall techniques, such as stateful inspection or application layer filtering, may be required.
Packet Filtering Router Examples
Example 1: Allow all incoming traffic from the IP address range 192.168.0.0/24 on port 80 (HTTP).
This rule allows all traffic from the IP address range 192.168.0.0 to 192.168.0.255 to pass through the router and reach the intended destination, as long as it is using the HTTP protocol on port 80. This might be useful if you want to allow web traffic from a specific subnet or network.
Example 2: Deny all incoming traffic from the IP address range 10.0.0.0/8 on port 22 (SSH).
This rule blocks all traffic from the IP address range 10.0.0.0 to 10.255.255.255 from reaching the protected network, as long as it is using the SSH protocol on port 22. This might be useful if you want to prevent unauthorized access to your network via the SSH protocol.
Example 3: Allow all outgoing traffic to the IP address 220.127.116.11 on port 53 (DNS)
This rule allows all traffic originating from the protected network and headed to the IP address 18.104.22.168 to pass through the router, as long as it is using the DNS protocol on port 53. This might be useful if you want to allow your network users to perform DNS queries and look up domain names.
I hope these examples give you an idea of how packet filtering routers work and how they can be used to control network traffic.
Advantages of Using Packet Filtering Router
Below are the advantages to use Packet Filtering Routers:
Efficient: Packet filtering routers are efficient at controlling network traffic because they only examine the headers of packets, rather than the entire payload.
This allows them to process large volumes of traffic quickly and with minimal impact on network performance.
Easy to Configure: Packet filtering routers are relatively easy to configure and maintain, especially for smaller networks.
They typically have a user-friendly interface that allows you to create and manage firewall rules quickly and easily.
Cost-Effective: Packet filtering routers are generally more affordable than other types of firewalls, making them a cost-effective option for small and medium-sized businesses if advance level data inspection isn’t required.
Basic Security: Packet filtering routers provide basic security for networks by allowing or denying specific types of traffic based on predefined rules.
Scalable: Packet filtering routers can be easily scaled to accommodate the needs of a growing network.
As your network expands, you can simply add more rules to your firewall/access policy to ensure that all traffic is properly controlled.
In summary, packet filtering routers offer an efficient, easy-to-use, cost-effective, and scalable solution for controlling network traffic and providing basic security for small and medium-sized networks.