Exam 300-101 topic 1 question 402 discussion

Actual exam question from Cisco's 300-101

Question #: 402
Topic #: 1

When unicast reverse path forwarding is configured on an interface, which action does the interface take first when it receives a packet?

A. It verifies that the source has a valid CEF adjacency.
B. It checks the egress access lists.
C. It verifies a reverse path via the FIB to the source.
D. It checks the ingress access lists.

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Suggested Answer: C 🗳️

by Phonnv at June 11, 2019, 8:08 a.m.

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soon

5 years, 5 months ago

should be - ingress access lists When a packet is received at the interface where Unicast RPF and ACLs have been configured, the following actions occur: Step 1: Input ACLs configured on the inbound interface are checked. Step 2: Unicast RPF checks to see if the packet has arrived on the best return path to the source, which it does by doing a reverse lookup in the FIB table. Step 3: CEF table (FIB) lookup is carried out for packet forwarding. Step 4: Output ACLs are checked on the outbound interface. Step 5: The packet is forwarded. Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2/security/configuration/guide/fsecur_c/scfrpf.html

upvoted 2 times

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Haggyman

5 years, 9 months ago

Phonny is correct. Keyword here is 'interface'. The interface checks the ingress ACL first.

upvoted 3 times

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Phonnv

6 years ago

Interface check acl first

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