Cisco Exam 350-501 Topic 3 Question 76 Discussion

Actual exam question for Cisco's 350-501 exam

Question #: 76
Topic #: 3

Refer to the exhibit.

The CE router is peering with both PE routers and advertising a public prefix to the internet. Routing to and from this prefix will be asymmetric under certain network conditions, but packets must not be discarded. Which configuration must an engineer apply to the two PE routers so that they validate reverse packet forwarding for packets entering their Gi2 interfaces and drop traffic from the RFC1918 space?

Aip verify unicast source reachable-via rx allow-default

Binterface GigabitEthernet 2
ip verify unicast source reachable-via rx

Cip verify unicast source reachable-via any allow-default
interface GigabitEthernet 2

Dip verify unicast source reachable-via any

Show Suggested Answer

Suggested Answer: D

by Kasandra at Oct 22, 2023, 04:06 AM

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Ahmed

8 months ago

You know, I'm starting to think this is one of those questions where the exam writers are just trying to trip us up. They probably want us to know the specific command for validating reverse packet forwarding, but they're throwing in a bunch of other stuff to make it more complicated. I'm going to have to really dig into the details on this one.

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Lisha

8 months ago

Alright, let's think this through. Option A seems to be the closest, but it's allowing default traffic, which might not be what we want. Option B is targeting the specific interface, but I'm not sure if that's enough. Option C is trying to cover both requirements, but the ordering of the commands might be off. And option D is just plain confusing.

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Felix

8 months ago

Hmm, this one's got me stumped. I can see the logic behind a few of the options, but I'm not confident that any of them are the right answer. I might need to review some of the routing concepts related to asymmetric routing and reverse packet forwarding.

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Ezekiel

8 months ago

This question seems pretty tricky. The key seems to be ensuring that the packets entering the PE routers' Gi2 interfaces are validated for reverse packet forwarding, while also dropping traffic from the RFC1918 space. I'm not sure which option is the best, but I'll give it a shot.

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