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Juniper Exam JN0-351 Topic 1 Question 33 Discussion

Actual exam question for Juniper's JN0-351 exam
Question #: 33
Topic #: 1
[All JN0-351 Questions]

You have DHCP snooping enabled but no entries are automatically created in the snooping database for an interface on your EX Series switch. What are two reasons for the problem? (Choose two.)

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Suggested Answer: B, C

The DHCP snooping feature in Juniper Networks' EX Series switches works by building a binding database that maps the IP address, MAC address, lease time, binding type, VLAN number, and interface information1.This database is used to filter and validate DHCP messages from untrusted sources1.

However, there are certain conditions that could prevent entries from being automatically created in the snooping database for an interface:

MAC limiting: If MAC limiting is enabled on the interface, it could potentially interfere with the operation of DHCP snooping.MAC limiting restricts the number of MAC addresses that can be learned on a physical interface to prevent MAC flooding attacks1. This could inadvertently limit the number of DHCP clients that can be learned on an interface, thus preventing new entries from being added to the DHCP snooping database.

Static IP address: If the device connected to the interface is configured with a static IP address, it will not go through the DHCP process and therefore will not have an entry in the DHCP snooping database1.The DHCP snooping feature relies on monitoring DHCP messages to build its database1, so devices with static IP addresses that do not send DHCP messages will not have their information added.

Therefore, options B and C are correct.Options A and D are not correct because performing a DHCPRELEASE would simply remove an existing entry from the database1, and Dynamic ARP inspection (DAI) uses the information stored in the DHCP snooping binding database but does not prevent entries from being created1.


Contribute your Thoughts:

Paz
27 days ago
Aha, I got it! The answer is B and D. Dynamic ARP inspection is the key here, gotta keep an eye on that ARP traffic!
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Dannette
8 days ago
A) The device that is connected to the interface has performed a DHCPRELEASE.
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Ressie
30 days ago
Haha, I bet the answer involves some kind of 'snooping' or 'inspection' gone wrong. These networking questions can be so sneaky!
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Buck
7 days ago
C) The device that is connected to the interface has a static IP address.
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Emmanuel
13 days ago
A) The device that is connected to the interface has performed a DHCPRELEASE.
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Skye
1 months ago
Hmm, I was leaning towards A and C, but B makes sense too. This is a tricky one!
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Rashad
8 days ago
User3: It's definitely a tricky situation, but I agree that all three options could be causing the problem.
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Celeste
9 days ago
User2: B could also be a possible reason for the problem.
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Brigette
15 days ago
User1: I think A and C are the reasons for the issue.
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Nathalie
2 months ago
I agree with you, that could be one reason. Another reason might be that MAC limiting is enabled on the interface.
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Lyda
2 months ago
I think the correct answers are B and C. If MAC limiting is enabled, DHCP snooping won't create any entries, and a device with a static IP address won't trigger DHCP snooping either.
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Amina
21 days ago
Yes, those are the two reasons for the problem with DHCP snooping entries not being created.
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Ashton
1 months ago
If both are true, then DHCP snooping won't create any entries.
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Casie
1 months ago
So, the correct answers are B and C then.
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Devora
1 months ago
Also, verify if the device connected has a static IP address.
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Goldie
1 months ago
Make sure to check if MAC limiting is enabled on the interface.
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Bernadine
1 months ago
I agree, B and C are the correct answers.
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Ma
1 months ago
That's true, a device with a static IP address won't trigger DHCP snooping either.
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Carman
1 months ago
I agree, MAC limiting can prevent DHCP snooping entries from being created.
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Ronald
2 months ago
I think the reason could be that the device has a static IP address.
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