# How does EIGRP calculate variance?

## How does EIGRP calculate variance?

EIGRP provides a mechanism to load balance over unequal cost paths throungh Variance Command. Variance is a number (1 to 128), multiplied by the local best metric then includes the routes with the lesser or equal metric. The default Variance value is 1, which means equal-cost load balancing.

What is variance in routing?

Variance is a term that is used in the EIGRP routing protocol. EIGRP selects a successor route and if certain criteria is matched, one or more feasible successors. These feasible successors are not actively used unless you use the variance command.

### How does EIGRP determine metric values?

The formula we use for the metric calculation looks like this:

1. Metric = [K1*bandwidth + ((K2*bandwidth)/(256-load))+K3*delay]
2. Metric = Metric*[K5/(reliability+K4)]
3. Metric = bandwidth (slowest link) + delay (sum of delays)
4. Metric = (107 / minimum bandwidth) * 256 + (sum of delays) * 256.

EIGRP load balancing By default, EIGRP supports equal-cost load balancing over four links. Equal-cost means that multiple routes must have the same metric to reach the destination, so that router can choose to load balance across equal cost links.

## How does EIGRP do unequal load balancing?

One magic word enables unequal-cost load balancing in EIGRP. The variance command is a multiplier and has a default value of 1. The router will multiple the Feasible Distance of the route by the variance value. Any feasible successor with a metric less than that new value will be entered into the routing table.

What is maximum path in EIGRP?

Like OSPF, EIGRP supports the ability to put multiple equal-metric routes in the routing-table. Like OSPF, EIGRP defaults to support four such routes for each subnet, and it can be configured to support up to 16 using the maximum-paths number EIGRP command.

### What is EIGRP summarization?

EIGRP supports automatic summarization which as the name implies means that it will automatically advertise summary routes to other EIGRP routers. EIGRP will check if you have any subnets that fall within the range of your network command(s) and if so, it will advertise the classful A, B or C network to its neighbors.

What is EIGRP in networking?

Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector routing protocol that is used on a computer network for automating routing decisions and configuration. EIGRP is used on a router to share routes with other routers within the same autonomous system.

## What factors are used in the metric calculations for EIGRP by default?

Metric calculation is a critical component for any routing protocol. EIGRP uses multiple factors to calculate the metric for a path. Metric calculation uses bandwidth and delay by default but can include interface load and reliability, too.

What does the variance command do?

The variance command multiplies the best cost (10,000) by 2 (20,000) and will begin load balancing across all paths with a FD less than that – which includes the path through R2(15,000). This will load balance the traffic in proportion to each path’s metric.

### How EIGRP will distribute traffic among multiple routes of unequal-cost?

Configuring EIGRP for Unequal-Cost Load Balancing A few words about configuring UCLB in EIGRP. You achieve this by setting the “variance” value to something greater than 1. EIGRP routing process will install all paths with metric < best_metric*variance into the local routing table.

What is EIGRP and how it works?

Introduction. This paper is an introduction to the Interior Gateway Routing Protocol (IGRP) suite of routing protocols designed and developed by Cisco Systems.

• Prerequisites. There are no specific requirements for this document.
• EIGRP Concepts.
• Compatibility Mode.
• DUAL Example.
• ## What are the k values represent In EIGRP?

Wide Metrics. The original EIGRP specifications measured delay in 10-microsecond (μs) units and bandwidth in kilobytes per second,which did not scale well with higher-speed interfaces.

• Metric Backward Compatibility. EIGRP wide metrics were designed with backward compatibility in mind.
• Interface Delay Settings.
• Custom K Values.