Common Address Redundancy Protocol


The Common Address Redundancy Protocol (CARP) is a computer networking protocol that allows multiple hosts on the same network segment to share an IP Address. It is primarily used for ensuring redundancy and fail-over, so in the event one host is unavailable, the others can continue to provide service. This makes it a crucial component for high availability and load balancing setups.


The International Phonetic Alphabet (IPA) phonetic transcription of the keyword “Common Address Redundancy Protocol” can be written as: /ˈkɒmən əˈdres rɪˈdʌndənsi prəˈtoʊkɒl/

Key Takeaways

<ol><li>Common Address Redundancy Protocol (CARP) is primarily used to allow multiple hosts on the same network segment to share an IP address. Its main purpose is to ensure that data is still available even if a server goes offline, thus enhancing the reliability and availability of network resources.</li><li>CARP is easily configurable, and provides failover redundancy that automatically switches to a backup or secondary server when the primary one fails. This automatic switch improves the fault tolerance of your system, thereby boosting overall system performance.</li><li>CARP is not bound to any specific operating system and is implemented in different open-source operating systems such as OpenBSD, FreeBSD, and Linux, amongst others. Therefore, it has broad compatibility and makes it an ideal choice for varied environments.</li></ol>


The Common Address Redundancy Protocol (CARP) is an extremely vital element in technology due to several reasons. Primarily, it consolidates safeguarded system availability and ensures seamless data access without interruptions, even if a failure occurs within the network. Its significant feature of providing redundancy by enabling multiple hosts on the same network segment to share an IP address, augments the fault tolerance while reducing the potential for a single point of failure. This aids in maintaining the operational efficiency and optimizing the uptime in a network infrastructure, making CARP a crucial aspect of network engineering and administration. It thereby contributes to providing robust, reliable and resilient network systems, preserving the integrity and continuity of business operations.


The Common Address Redundancy Protocol (CARP) is predominantly used to ensure that networks and services are continuously available even if a particular hardware device or network component fails. One primary purpose of this technology is to provide a fail-proof mechanism that ensures seamless service delivery by enabling multiple hosts on the same network segment to share an IP address. The role of this shared IP address is crucial because it eliminates what would otherwise be a singular point of failure within a network. This way, if one device goes offline or is affected, another device within the network can readily replace it, ensuring that the service remains uninterrupted.Moreover, CARP comes into play as a highly effective solution in Load Balancing. In scenarios where there is heavy network traffic, CARP distributes data demands across many different servers, thus decreasing the chance of any single server becoming a bottleneck and slowing down service delivery. By doing so, it enhances the overall efficiency and reliability of a network. In essence, CARP is vital for maintaining business continuity and high availability of services in a networked environment, particularly in businesses where network service disruptions could result in significant financial or operational loss.


Common Address Redundancy Protocol (CARP) is a protocol that allows multiple hosts to share the same IP address, providing fault-tolerance and high availability. Here are three real-world examples:1. Firewall Clustering: Firewalls use CARP to eliminate single points of failure by allowing multiple firewalls to share a ‘virtual’ common IP address. If one firewall fails, another takes over seamlessly without affecting the network system. For example, the firewall system used by organizations to secure network traffic usually applies CARP for high availability and load balancing.2. Server Load Balancing: In the world of web server hosting, CARP is typically used for achieving load balancing. It’s quite common with high-traffic websites. Multiple servers hosting the same website share a common IP address via CARP. Visitors are directed to different servers to balance the load, and if one server crashes, other servers can take over seamlessly maintaining the availability of the website.3. Internet Service Providers (ISP): ISPs often use CARP to implement redundancy in their network infrastructure. They have multiple routers and servers sharing common IP addresses. If one system fails, traffic can be re-routed through another system without causing service disruption for the end-users.

Frequently Asked Questions(FAQ)

Q: What is Common Address Redundancy Protocol (CARP)?A: CARP is a protocol that allows multiple hosts to share the same IP address and MAC address, providing failover redundancy. Its primary purpose is to ensure that data traffic is always available by serving as a backup if the primary machine fails.Q: How does CARP work?A: CARP operates through a system of a master device and one or more backup, or redundant devices. If the master device fails, one of the backup devices takes over immediately. Q: What are the benefits of using CARP?A: CARP allows high availability and failover protection for network resources. It prevents downtimes in critical systems by allowing a secondary device to seamlessly take over in the case of a system failure.Q: Where is CARP commonly used?A: CARP is commonly used in circumstances where system uptime is of great importance, like database servers, file servers, websites, and email servers.Q: Is CARP an open-source protocol?A: Yes, CARP is an open-source protocol, which means that it’s freely available for use and modification.Q: How is CARP different from VRRP?A: While both CARP and VRRP provide IP address and network path redundancy, there are a few key differences. VRRP is a standard protocol, while CARP is an open-source protocol. Also, CARP supports more advanced features like load balancing and is generally considered more secure.Q: What are the requirements to implement CARP?A: To implement CARP, you need at least two servers or devices capable of running the protocol, as well as network infrastructure that can support multicast traffic. You also need to configure the devices in the CARP group with the same virtual IP address.Q: Can I use CARP for load balancing?A: Yes, CARP can be used for load balancing. It’s especially useful in distributing network traffic among multiple servers to ensure smooth functionality even with high traffic demand.

Related Finance Terms

  • Failover
  • Redundancy
  • IP Addressing
  • Network Interfaces
  • Load Balancing

Sources for More Information


About The Authors

The DevX Technology Glossary is reviewed by technology experts and writers from our community. Terms and definitions continue to go under updates to stay relevant and up-to-date. These experts help us maintain the almost 10,000+ technology terms on DevX. Our reviewers have a strong technical background in software development, engineering, and startup businesses. They are experts with real-world experience working in the tech industry and academia.

See our full expert review panel.

These experts include:


About Our Editorial Process

At DevX, we’re dedicated to tech entrepreneurship. Our team closely follows industry shifts, new products, AI breakthroughs, technology trends, and funding announcements. Articles undergo thorough editing to ensure accuracy and clarity, reflecting DevX’s style and supporting entrepreneurs in the tech sphere.

See our full editorial policy.

More Technology Terms

Technology Glossary

Table of Contents