EIGRP Overview and Features

EIGRP (Enhanced Interior Gateway Routing Protocol) is an advanced distance-vector routing protocol developed by Cisco. It is known for its rapid convergence, efficient use of network bandwidth, and support for various network layer protocols.

Key Features:

• DUAL (Diffusing Update Algorithm): EIGRP uses DUAL to ensure loop-free paths and fast convergence. DUAL allows EIGRP to find backup paths (feasible successors) instantly, reducing convergence time significantly.
• Partial and Bounded Updates: Unlike traditional distance-vector protocols that send full routing tables periodically, EIGRP sends only partial updates (only changes) and only to affected routers, reducing bandwidth consumption.
• Reliable Transport Protocol (RTP): EIGRP uses RTP for guaranteed delivery of EIGRP packets. RTP supports both unicast and multicast transmissions.
• Neighbor Discovery/Recovery: EIGRP uses Hello packets to discover neighbors and maintain neighbor relationships.
• Support for VLSM/CIDR: EIGRP fully supports Variable Length Subnet Masking (VLSM) and Classless Inter-Domain Routing (CIDR).
• Multiple Network Layer Support: EIGRP can route IP, IPX, and AppleTalk, although its primary use today is for IP routing.
• Unequal Cost Load Balancing: EIGRP can load balance traffic across multiple paths with unequal costs, which is a significant advantage over protocols like OSPF.