# EIGRP Variance

Video Activity

EIGRP Variance Now we cover a subtopic, Variance. This lesson helps us understand the concept of variance and what its role is in the EIGRP process. Since EIGRP sends equal amounts of traffic over each link. You'll learn about its capacity to send unequal amounts of traffic over each link, and how to calculate out that metric of a successor route f...

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Time
15 hours 34 minutes
Difficulty
Intermediate
CEU/CPE
16
Video Description

EIGRP Variance Now we cover a subtopic, Variance. This lesson helps us understand the concept of variance and what its role is in the EIGRP process. Since EIGRP sends equal amounts of traffic over each link. You'll learn about its capacity to send unequal amounts of traffic over each link, and how to calculate out that metric of a successor route for any route that's in the routing table.

Video Transcription
00:04
The next topic of discussion is a gr Bavarians. Now EJ RP can send equal amounts of traffic
00:12
over multiple links if the metrics match. So if there are three links president between source and destination and they have the exact same feasible distance E Aguilar people install all three routes in the routing table and send equal amounts of traffics or each route over each link.
00:32
This is called equal cost load sharing.
00:35
Yeah, therapy also has the capacity to do unequal cost. Load sharing
00:41
through a concept called variance Now variances a multiplier for the feasible distance off a successor route in rib.
00:49
So variance is a multiplier for the feasible distance or the metric off successor route in the routing table.
00:57
Any route in the topology table, with the metric or feasible distance less than the product off the feasible distance and variance is also installed in the routing table or route information base or rib.
01:10
Once again, any route in the topology table
01:12
or any route that is a feasible successor that is sitting in the topology table
01:19
with a metric that is less than the product off your feasible distance off the successor out and variance is also installed in the route information base or your outing table.
01:32
The default variance is one and again range between one and 1 28
01:38
So what do I mean by
01:40
this statement? Over here,
01:42
the product of feasible distance and variance. Okay, so let's look at this diagram over here.
01:48
Router one has two paths to network 10.
01:52
Both paths past the feasibility condition because
01:57
the top route is your successor out
02:00
with a total distance or feasible distance off 10 plus five
02:05
15 and the reported distance is less than
02:08
my feasible distance,
02:10
So their distance that router to is reporting to router one is less than total 15
02:17
for the bottom route. Also, my reporter distance router to is reporting to Router one. It's five, which is less than 15 so both routes get installed in the topology table
02:29
than the top one. Since it has a total distance of 15 worsens. The bottom one, with a total distance of 20
02:36
gets installed in the routing table,
02:38
so the top route goes in the topology table and then from the topology table to the routing table for use.
02:45
Now, since the variance is set to won by default. That's the only route that'll be installed in the routing table.
02:53
The bottom route will sit in the topology table because it is a feasible successor.
02:57
However, if I want also, install this bottom route in my routing table for unequal cost load sharing so that I can send traffic over both the links traffic proportional to the metric off each link.
03:12
What I can do is
03:15
I can pick a variance off, too.
03:19
So if variants, I pick us too. And variance is a multiplier for my feasible distance and my feasible distance off. My successor out here is
03:29
15
03:30
so feasible distance is 15
03:37
15 times two equals 30. So if I set my variance to two,
03:43
any route that has a feasible distance in the topology table any feasible successor out with a feasible distance less than 30 will also get installed in the routing table. So the bottom route right now is sitting in the topology table with the distance off 15 plus five, which is 20.
04:01
If I increase the variants
04:02
two
04:04
two from one,
04:06
you get a product that is 30 since 20 years, less than 30. The bottom route also gets installed in the routing table and traffic proportional to the metric off. Each path is sent over each link.
04:20
This concludes the variance lecture.
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