Discuss Cisco 350-501 Exam Topic 4 Question 132

While implementing TTL security, an engineer issues the PE(config-router-af)#neighbor 2.2.2.2 ttl-security hops 2 command. After issuing this command, which BGP packets does the PE accept?

Afrom 2.2.2.2, with a TTL of less than 2

Bto 2.2.2.2, with a TTL of less than 253

Cfrom 2.2.2.2, with a TTL of 253 or more

Dto 2.2.2.2, with a TTL of 2 or more

Suggested Answer: C

Thettl-security hops <number>command sets the maximum number of hops that a BGP message can traverse. In this case, settingttl-security hops 2means that the router will accept BGP packets from a neighbor (2.2.2.2) only if the TTL is 253 or more. This is because the default TTL value is 255, and for each hop, the TTL is decremented by 1. Therefore, a packet from a directly connected neighbor would have a TTL of 254 when it reaches the PE router. If the packet has traversed one more router (making it two hops away), the TTL would be 253 upon arrival.

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12 comments · newest first

Vicki 1 month ago

I’m leaning towards A. Lower TTL means they’re closer, right?

Timothy 2 months ago

I feel like option D makes sense too. It’s about the packets sent to the neighbor.

Nohemi 2 months ago

I think it's option C. Only packets with high TTL should be accepted.

Nathalie 2 months ago

Yeah, I agree with C. That's how TTL security works!

Roxane 2 months ago

Just to clarify, it's about incoming packets, not outgoing.

Raina 2 months ago

Wait, are we sure about that? Sounds off to me.

Jerry 2 months ago

I think it's D. TTL of 2 or more makes sense.

Stefania 3 months ago

It's definitely C, right? TTL of 253 or more.

Paris 3 months ago

I thought the command was supposed to allow packets with a higher TTL, so I'm thinking option C makes sense, but I could be wrong.

Shannan 3 months ago

I feel like the TTL security is meant to prevent packets from too far away, so maybe it's option D? But I can't recall the exact details.

Alysa 3 months ago

I think we practiced a similar question where we had to determine which packets were accepted based on TTL settings. I might lean towards option C.

Lynsey 3 months ago

I remember something about TTL values, but I'm not sure if it's about accepting packets or rejecting them.

Cisco 350-501 Exam - Topic 4 Question 132 Discussion