EIGRP (Enhanced Interior Gateway Routing Protocol)

EIGRP (Enhanced Interior Gateway Routing Protocol) is a It is a hybrid routing protocol that show both distance vector and link-state routing protocol properties. EIGRP (Enhanced Interior Gateway Routing Protocol) was developed by Cisco as a Cisco proprietary protocol and it is only available on Cisco devices.

EIGRP (Enhanced Interior Gateway Routing Protocol) is a classless routing protocol. It sends the subnet masks in the update packets. EIGRP also supports VLSM (Variable Length Subnet Mask), so EIGRP uses the IP addresses range very efficent.

The most important characteristic of EIGRP is that, it is a fast converged routing protocol. EIGRP keeps the “Backup Routes” beside the “Best Route” to a destination. So, during a failure, EIGRP does not need to calculate a new route. Instead, EIGRP uses the Backup Route. This provides to EIGRP, Faster Convergence mechanism.

EIGRP (Enhanced Interior Gateway Routing Protocol) uses a very complex metric by using bandwith, delay, load, reliability and MTU values. This formule is showed below:

EIGRP Configuration with Packet Tracer

EIGRP Metric Formula

As you can see, there are some K values in EGRP metric formule. By default these values are:

K1 (Bandwidth) = 1
K2 (Load) = 0
K3 (Delay) = 1
K4(Reliability) = 0
K5(MTU) = 0

These K values need to be match in both ends to form an EIGRP Neighbourship. You can change these values but it is not recommended.

By default Bandwith and Delay values become important only and used as a metric ( The other parts will be 0, becaue of multiplying with 0). So, we can say that, EIGRP (Enhanced Interior Gateway Routing Protocol) uses the path with minimum bandwidth and the total delay to a destination.

Bandwidth = 107/Bandwidth in Kbps
Delay = Delay / 10

The defalut Formula becomes like below (with default K values ) :

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Lesson tags: EIGRP, routing
Back to: CCIE > EIGRP

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