EIGRP

EIGRP (Enhanced Interior Gateway Routing Protocol) is a Cisco proprietary hybrid routing protocol that combines characteristics of both distance-vector and link-state routing protocols. It was designed to overcome the limitations of traditional distance-vector routing protocols and to provide better performance, scalability, and convergence time.

EIGRP uses a hierarchical network design and is suited for medium to large enterprise networks. It supports classless routing and variable-length subnet masking (VLSM), which allows for efficient use of IP address space. EIGRP also supports load balancing and multiple paths to a destination, which can improve network performance.

EIGRP uses a metric called “composite metric” to calculate the best path to a destination. The composite metric is a combination of bandwidth, delay, reliability, load, and maximum transmission unit (MTU) of the path. EIGRP also uses a feature called “feasible successor” to provide fast convergence and loop prevention.

EIGRP can be configured to support multiple network layer protocols, including IP, IPX, and AppleTalk. It also supports authentication and encryption for secure routing. EIGRP uses a sophisticated neighbor discovery and adjacency process called “Dual” (Diffusing Update Algorithm), which allows for fast convergence and efficient use of network resources.