NOTE By default, traf?¬?c is distributed proportionately among the links with unequal costs,
with respect to the metric.
Implementing EIGRP 183
Example: Variance
In Figure 5-6, a variance of 2 is con?¬?gured, and the range of the metric values, which are the
feasible distances for Router E to get to network 172.16.0.0, is 20 to 45. This range of values
determines the feasibility of a potential route.
Figure 5-6 Variance Example
A route is feasible if the next router in the path is closer to the destination than to the current router
and if the metric of the alternate path is within the variance. Load balancing can use only feasible
paths, and the routing table includes only these paths. The two feasibility conditions are as follows:
?– The local best metric, which is the current feasible distance, must be greater than the best
metric (the advertised distance) that is learned from the next router. In other words, the next
router in the path must be closer to the destination than to the current router; this criterion
prevents routing loops.
?– The metric of the alternate path must be less than the variance multiplied by the local best
metric (the current feasible distance).
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