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Exam 300-410 topic 1 question 491 discussion

Actual exam question from Cisco's 300-410

Question #: 491
Topic #: 1

Refer to the exhibit.

A network engineer troubleshooting a packet drop problem for the host 172.16.100.5 notices that only one link is used and installed on the routing table, which saturates the bandwidth. Which action must the engineer take to resolve the high bandwidth utilization problem and share the traffic toward this host between the two available links?

A. Disable the eigrp split horizon loop protection mechanism.
B. Set the eigrp variance equal to 3 to install a second route with a metric not larger than 3 times of the best metric.
C. Change the EIGRP delay metric to meet the feasibility condition.
D. Set the eigrp variance equal to 4 to install a second route with a metric not larger than 4 times of the best metric.

Show Suggested Answer

Suggested Answer: C 🗳️

by Brand at Sept. 7, 2023, 7:13 p.m.

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Colmenarez

Highly Voted 1 year, 10 months ago

Selected Answer: C

variance 2 is already in place. we need to meet the feasibility condition first.

upvoted 9 times

bk989

11 months, 2 weeks ago

upvoted 3 times

test190502

9 months, 3 weeks ago

It's right at the beginning. ーーーーーーーーーーー router eigrp 1 variance 2 ーーーーーーーーーーー

upvoted 2 times

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Colmenarez

1 year, 10 months ago

AD of FS (409600) is not lower than FD of the successor (409600)

upvoted 1 times

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bk989

Most Recent 11 months, 2 weeks ago

It is C. The reported distance of feasible successor is NOT LOWER than our successor. If we lower the delay by just enough to lower the reported distance and metric we do not need to worry about variance. I don't see where it says variance is 2. There is no variance shown in the output. If we changed variance to 100000 it wouldn't make a difference because reported distance of feasible successor is equal to our metric which doesn't guarantee a loop free path.

upvoted 1 times

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[Removed]

1 year ago

Selected Answer: C

C is correct

upvoted 1 times

[Removed]

12 months ago

409600 is the same on both routers, but the delay is not, which must be matched.

upvoted 1 times

bk989

11 months, 2 weeks ago

the delay does not need to be"matched". It needs to be lowered on the feasible successor candidate so the rported distance and feasible distance (of feasible successor) can be lowered

upvoted 1 times

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2581c6a

1 year, 1 month ago

Option C: Changing the EIGRP delay metric is not necessary. The metrics are already within range for load balancing.

upvoted 1 times

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bk989

1 year, 4 months ago

The RD of s2/0 is 409600. it needs to be 409599 to be lower thean the FD of the best route. So we need change a metric. The easiest, and usually recommended is to change delay and not bandwidth. Also delay is differenct in the output.

upvoted 2 times

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AlexInShort12

1 year, 7 months ago

Selected Answer: B

With the variance to 2, the RT should already load balance between the two routes... The feasibility condition doesn't talk about the delay only the FD-AD.... Probably something wrong with the question.

upvoted 1 times

bk989

1 year, 6 months ago

the feasible distance of the serial interface is the exact same thing as the reported distance of eth1/0. So changing variance wont matter, as it needs to be lower. if it is lower, eigrp knows the backup route wont point back to the current router, because - the feasible distance metric is lower. If it is the same feasible distance or higher, there is a chance the route points back to this router. So in the scenario above we changed delay metric to slightly lower the feasible distance in the serial interface.

upvoted 1 times

bk989

1 year, 6 months ago

think about it. If the FD metric is higher than the RD metric there is a chance the exact same routing path is encapsulated in a bigger routing path. If it is lower there is no chance of this happening, unless we really are modifying alot of the metrics on each individual router throughout the topology.

upvoted 1 times

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louisvuitton12

1 year, 9 months ago

Selected Answer: C

It is C for me

upvoted 2 times

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chris110

1 year, 10 months ago

Selected Answer: C

From the output of the “show ip eigrp topology …” command, we notice network 172.16.100.5/32 was learned via two routes: + From 10.4.1.5 with FD = 409600 and AD = 128256 + From 10.3.1.6 with FD = 435200 and AD = 409600 To use both paths (called unequal cost load balancing) with EIGRP, the second path must satisfy the feasibility condition. The feasibility condition states that, the Advertised Distance (AD) of a route must be lower than the feasible distance of the current successor route. In this case, the second path did not satisfy the feasible condition as its AD (409600) is equal to the FD of the best path -> Therefore we cannot configure load balancing with “variance” command.

upvoted 3 times

chris110

1 year, 10 months ago

The only reasonable solution of this question is “change the delay metric” so that the value of the FD of the best path is higher than its current value to meet the feasibility condition. Suppose after changing the delay metric, the second path now met feasibility condition. Let’s check if the second path would be installed into the routing table: The EIGRP will install all paths with metric < variance * best_metric into the local routing table. Therefore we can calculate the variance > metric / best_metric = 435200 / 409600 =1.06 -> A variance of 2 is enough to make EIGRP install the second path to its routing table.

upvoted 1 times

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Brand

1 year, 11 months ago

It looks to me that variance = 3 would do the trick as well.

upvoted 2 times

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