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Cisco 300-420 Exam - Topic 10 Question 111 Discussion

An engineer is designing a PIM Anycast RP solution between two data centers. The design must ensure that RP1 in DC1 and RP2 in DC2 inform each other about specific sources that have joined locally. Which solution must the engineer choose?
B) Enable MSDP between RPs using separate unique loopback interfaces
A) Provision the RPs on the same IP subnet and extend the subnet at Layer 2 between data centers
C) Enable MSDP between RPs using the configured Anycast RP address
D) No action is required because PIM registers from the source will, by default, reach each RP

Cisco 300-420 Exam - Topic 10 Question 111 Discussion

Actual exam question for Cisco's 300-420 exam
Question #: 111
Topic #: 10
[All 300-420 Questions]

An engineer is designing a PIM Anycast RP solution between two data centers. The design must ensure that RP1 in DC1 and RP2 in DC2 inform each other about specific sources that have joined locally. Which solution must the engineer choose?

Show Suggested Answer Hide Answer
Suggested Answer: B

In Anycast RP, two or more RPs are configured with the same IP address on loopback interfaces. The Anycast RP loopback address should be configured with a 32-bit mask, making it a host address. All the downstream routers should be configured to 'know' that the Anycast RP loopback address is the IP address of their local RP. IP routing automatically will select the topologically closest RP for each source and receiver.

MSDP used for Anycast RP is an intradomain feature that provides redundancy and load-sharing capabilities. Enterprise customers typically use Anycast RP for configuring a Protocol Independent Multicast sparse mode (PIM-SM) network to meet fault tolerance requirements within a single multicast domain.

https://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/ip_multicast/White_papers/anycast.html#wp1029118

https://www.cisco.com/c/en/us/support/docs/ip/ip-multicast/115011-anycast-pim.html

' You need to have a loopback on each prospective RP router, which is different than the loopback that is being used as the RP address.'


by Helga at May 03, 2025, 11:22 PM

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Titus
8 months ago
C seems plausible, but I’d stick with B for clarity.
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Lawana
9 months ago
Definitely agree with B! It’s the standard approach.
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Irving
9 months ago
I think B is the right choice. MSDP is key here.
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Leonor
9 months ago
Wait, can D really be true? Sounds too easy!
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Erick
9 months ago
A is not a good idea; you need separate RPs for redundancy.
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Colette
9 months ago
I vaguely recall that Anycast RP setups usually require some form of MSDP to communicate, so I might lean towards option C, but I need to double-check that.
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Jamal
10 months ago
I’m a bit confused about option D. I thought PIM would handle the registration automatically, but I’m not sure if that applies in this scenario.
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Annett
10 months ago
I practiced a similar question where we had to decide on MSDP configurations, and I feel like option B makes more sense since it mentions unique loopback interfaces.
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Simona
10 months ago
I think I remember that MSDP is important for RPs to share source information, but I'm not sure if it's about using loopback interfaces or the Anycast address.
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Lemuel
10 months ago
Hmm, I'm not sure if just relying on the default PIM register behavior is enough for this design. I think we need to set up some kind of RP coordination.
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Annice
11 months ago
I'm pretty confident that enabling MSDP between the RPs is the way to go here. Option C seems like the right choice.
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Mabel
11 months ago
I'm a bit confused on the differences between the MSDP options. I'll need to review the details on how each one works.
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Matthew
11 months ago
Okay, let's see. I think the key is ensuring the RPs can communicate with each other about the sources. Option B looks promising.
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Zona
11 months ago
This seems like a tricky one. I'll need to think through the PIM Anycast RP design carefully.
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Deangelo
1 year ago
Option C is the way to go, but I like Nichelle's sense of humor. Sometimes the simplest solution is the best, even if it's not the most 'engineered'.
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Nichelle
1 year ago
Haha, D is the real winner here. Why bother with all that MSDP setup when the sources can just find the RPs on their own?
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Carmelina
1 year ago
User 4: True, it's always good to have a backup plan just in case.
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Grover
1 year ago
User 3: But what if there are issues with the default setup?
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Stefany
1 year ago
User 2: Yeah, why make it more complicated with MSDP when it's not necessary?
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Britt
1 year ago
User 1: I think D is the best option here.
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Willis
1 year ago
Wait, are we sure we can't just extend the subnet and let the RP registers figure it out? Option A sounds like the lazy but effective solution.
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Galen
1 year ago
Yeah, option B would provide a more secure solution for the PIM Anycast RP design.
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Brianne
1 year ago
I agree, enabling MSDP between RPs using separate loopback interfaces seems like a safer choice.
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Tammy
1 year ago
I think option A could work, but what about the potential for network loops?
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Louvenia
1 year ago
I'm not sure, but I think D could also be a valid option since PIM registers from the source will reach each RP by default.
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Casey
1 year ago
I disagree, I believe the correct answer is C, enabling MSDP between RPs using the configured Anycast RP address.
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Jackie
1 year ago
I'm leaning towards C. Using the Anycast RP address for MSDP just seems more straightforward, doesn't it?
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Tammi
1 year ago
C) Enable MSDP between RPs using the configured Anycast RP address
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Rikki
1 year ago
B) Enable MSDP between RPs using separate unique loopback interfaces
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Jamie
1 year ago
A) Provision the RPs on the same IP subnet and extend the subnet at Layer 2 between data centers
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Jettie
1 year ago
I think the answer is B, enabling MSDP between RPs using separate unique loopback interfaces.
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Elza
1 year ago
Option B seems like the way to go. MSDP between RPs using separate loopback interfaces sounds like the most reliable approach.
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Gail
1 year ago
User 3: It seems like a solid solution to make sure the RPs in both data centers can inform each other about specific sources.
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Adelaide
1 year ago
User 2: I agree, having separate loopback interfaces can help ensure better communication between the RPs.
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Lilli
1 year ago
User 1: I think option B is the best choice. Using separate loopback interfaces for MSDP between RPs sounds reliable.
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