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Exam 400-007 topic 1 question 77 discussion

Actual exam question from Cisco's 400-007
Question #: 77
Topic #: 1
[All 400-007 Questions]


Refer to the exhibit. Traffic was equally balanced between Layer 3 links on core switches SW1 and SW2 before an introduction of the new video server in the network. This video server uses multicast to send video streams to hosts and now one of the links between core switches is over utilized. Which design solution solves this issue?

  • A. Aggregate links using Layer 2 link aggregation.
  • B. Add more links between core switches.
  • C. Apply a more granular load-balancing method on SW2.
  • D. Filter IGMP joins on an over-utilized link.
  • E. Apply a more granular load-balancing method on SW1.
Show Suggested Answer Hide Answer
Suggested Answer: E 🗳️
by Leon_Wang at Feb. 2, 2023, 6:29 a.m.

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Nery
1 week, 6 days ago
Selected Answer: C
Answer is C..By applying a more granular load-balancing method on SW2, you can ensure that traffic is more evenly distributed between the Layer 3 links, preventing one link from becoming over-utilized due to the new multicast video traffic. This method would help optimize the traffic distribution across available links and address the issue without necessarily requiring additional physical resources.
upvoted 1 times
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sandccie
1 month, 2 weeks ago
Selected Answer: E
E. the ip multicast mulitpath command should apply to the router near the receiver end.
upvoted 1 times
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caleb
8 months, 2 weeks ago
Selected Answer: E
i voted E ECMP multicast load spitting has to be enable on the receivers gateway router in this SW1 that is the one doing rpf to find links going to the source https://www.cisco.com/c/en/us/td/docs/ios/12_4t/ip_mcast/configuration/guide/mctlsplt.html#wp1055334
upvoted 3 times
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Rollizo
9 months ago
Selected Answer: C
ECMP multicast load splitting method based on source, group, and next-hop address--You can configure ECMP multicast load splitting using the ip multicast multipath command with the s-g-hash and next-hop-based keywords. (multicast multipath)
upvoted 1 times
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VeeG
11 months, 1 week ago
Single link is utilised as RPF check has been on single L3 Interface. How Layer 3 RPF check can get redistributed over layer2 link aggregation.
upvoted 1 times
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Akkisingh
1 year, 5 months ago
Selected Answer: A
it's coz of RPF, need either a GRE tunnel or L2 aggregation
upvoted 2 times
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Alionzo
1 year, 6 months ago
IP multicast Multipath only split load from more than one source, in this case, there is only one source neither E or C is correct as traffic will still Continuing To hit overutilized link. A is correct
upvoted 1 times
rvzA
1 year, 6 months ago
The key is multicast and "streamS", one video stream is 1 channel (ip/port), so it will be multiple IP/Port pairs for all the streams coming from the server. Changing the hashing at SW2 is the correct answer.
upvoted 1 times
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Dvnn
1 year, 7 months ago
Selected Answer: E
ip multicast multipath applies to the device which is closer to the receiver. So if this question is about this command, then the answer is E. https://www.cisco.com/c/en/us/td/docs/ios/12_4t/ip_mcast/configuration/guide/mctlsplt.html "Be sure to enable the ip multicast multipath command on the router that is supposed to be the receiver for traffic from more than one incoming interfaces, which is opposite of unicast routing. From the perspective of unicast, multicast is active on the sending router connecting to more than one outgoing interfaces."
upvoted 3 times
main_street
1 year, 6 months ago
Agreed E is correct https://www.fragmentationneeded.net/2010/10/load-balancing-ip-multicast-flows.html
upvoted 1 times
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pizdecvsemu
1 year, 7 months ago
Selected Answer: A
With no L2 aggregation the only option is ECMP load splitting, and it's not load balancing.
upvoted 3 times
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ying162
1 year, 7 months ago
I have done some more reading andsince the links are already L3, we can use "ip multicast multipath" on SW2 to do the load balancing. Layer 2 etherchannel will not help as the default load balancing hash is src-mac. C is the way to go then.
upvoted 1 times
Leon_Wang
1 year, 7 months ago
in my opinion, "ip multicast multipath" should apply on both SW1 and SW2 according official document. And the default loadbance of the portchannel with IP is ip and l4port. Nexus9000# show port-channel load-bal System config: Non-IP: src-dst mac IP: src-dst ip-l4port rotate 0
upvoted 1 times
ying162
1 year, 7 months ago
the aggregation is L2 though as per A
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biddid
1 year, 6 months ago
No need to use default value. You can change the load balance method after aggregration. A is more appropriate.
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ying162
1 year, 8 months ago
I think C makes sense
upvoted 2 times
ying162
1 year, 7 months ago
A makes more sense. The outgoing interface from SW2 will be the port-channel and the hashing algorithm will take care of the load balancing
upvoted 1 times
ying162
1 year, 7 months ago
ignore this message
upvoted 1 times
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Leon_Wang
1 year, 8 months ago
Selected Answer: C
I think C
upvoted 2 times
Leon_Wang
1 year, 8 months ago
Correct the answer maybe only A https://www.cisco.com/c/zh_cn/support/docs/ip/ip-multicast/16450-mcastguide0.html#anc17
upvoted 2 times
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