EIGRP

EIGRP Definition

EIGRP (Enhanced Interior Gateway Routing Protocol) is a robust and efficient dynamic routing protocol used in computer networks. It enables routers to share information about the network's topology and automatically adjust routes based on the best available path to a destination.

How EIGRP Works

EIGRP works by propagating routing information among connected routers. It employs the Diffusing Update Algorithm (DUAL) to calculate the best routes to different network destinations. EIGRP takes into account various metrics, such as bandwidth, delay, load, reliability, and Maximum Transmission Unit (MTU), to determine the optimal path.

The protocol utilizes Reliable Transport Protocol (RTP) to ensure reliable and ordered delivery of routing updates, enhancing the efficiency and resilience of the network. EIGRP routers exchange information via Hello packets periodically to discover their neighboring routers and establish adjacencies. Once the adjacencies are formed, the routers share routing updates only with the routers they are directly connected to. This selective update mechanism increases scalability and reduces network overhead.

EIGRP utilizes two types of routing tables: the Neighbor Table and the Topology Table. The Neighbor Table maintains information about directly connected routers, including their IP addresses and reliability. The Topology Table contains detailed topological information about the network, including feasible successor routes, which are backup routes that can be used if the primary route fails.

Key Features of EIGRP

  • Fast Convergence: EIGRP supports the concept of successor routes and feasible successor routes, allowing for rapid convergence when a particular route fails. Successor routes are the primary routes chosen to forward traffic, while feasible successor routes serve as backup paths that can be immediately utilized if the primary route becomes unavailable. This feature reduces network downtime and ensures efficient routing.

  • Load Balancing: EIGRP provides sophisticated load balancing capabilities to evenly distribute traffic across multiple paths. This helps optimize network performance and prevent congestion on specific links, enabling more efficient resource utilization.

  • Loop-Free Path Selection: EIGRP guarantees loop-free path selection by utilizing the DUAL finite-state machine. This algorithm ensures that a routing loop does not occur during convergence. The DUAL algorithm computes the best path to a destination based on a composite metric that considers bandwidth, delay, load, reliability, and MTU.

Prevention Tips

To ensure the security and integrity of an EIGRP-enabled network, consider the following best practices:

  • Access Control Lists (ACLs): Implement access control lists to restrict unauthorized access to EIGRP routing information. By filtering incoming and outgoing packets, ACLs help protect sensitive routing information from potential threats.

  • Secure Passwords: Utilize strong and unique passwords for EIGRP configuration, authentication, and user access. Implement a password policy that enforces regular password updates and discourages the use of common or easily guessable passwords.

  • Configuration Auditing: Regularly monitor EIGRP routing tables and audit configuration changes to detect any unauthorized modifications. Implement a change management process that includes thorough documentation and validation of configuration changes.

  • Authentication: Implement authentication mechanisms, such as Message Digest Algorithm 5 (MD5), to ensure that only trusted routers can participate in EIGRP updates. Authentication helps verify the authenticity and integrity of routing updates, preventing the dissemination of malicious or forged routing information.

For more information about related terms, refer to the following glossary definitions:

  • Routing Protocol: A protocol that specifies how routers communicate with each other and share information to determine the best paths for forwarding network traffic.
  • Dynamic Routing: A routing process that automatically adjusts to changing network conditions by using routing protocols like EIGRP.

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