Cisco Exam 300-420 Topic 10 Question 111 Discussion

Actual exam question for Cisco's 300-420 exam

Question #: 111
Topic #: 10

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?

AProvision the RPs on the same IP subnet and extend the subnet at Layer 2 between data centers

BEnable MSDP between RPs using separate unique loopback interfaces

CEnable MSDP between RPs using the configured Anycast RP address

DNo action is required because PIM registers from the source will, by default, reach each RP

Show Suggested 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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Willis

9 days 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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Louvenia

12 days 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

13 days ago

I disagree, I believe the correct answer is C, enabling MSDP between RPs using the configured Anycast RP address.

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1 months 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

4 days 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

5 days ago

User 2: I agree, having separate loopback interfaces can help ensure better communication between the RPs.

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Lilli

8 days 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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