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Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance vector routing protocol based on the principles of the Interior Gateway Routing Protocol (IGRP).
EIGRP is a successor to the Interior Gateway Routing Protocol (IGRP). Both are owned by Cisco and operate only on their devices. Cisco introduced EIGRP because it needed a protocol with faster converging abilities, route selection and calculation and the ability to record information from neighboring devices.
Techopedia Explains Enhanced Interior Gateway Routing Protocol
EIGRP has the following characteristics:
- Advanced operational efficiency
- Capabilities of both link state and distance vector
- A classless routing protocol
- Unique features including use of Reliable Transport Protocol (RTP), a diffusing update algorithm (DUAL), updates and updated information about neighbors
- Faster converging because it precalculates routes and does not broadcast hold-down timer packets before converging
EIGRP uses bandwidth, delay, load and reliability to calculate the metric for its routing table (not hop count used by legacy protocols). For this reason, EIGRP always selects and calculates the most optimal route for efficiency. EIGRP uses a DUAL algorithm to avoid loops and send occasional hello packets to check the status of neighbor routers.
