The correct answer is that DHCP option 150 provides the IP address of a TFTP server to DHCP clients, and in a Cisco VoIP environment, this is the standard mechanism used by IP phones to locate the TFTP server from which they download their configuration and firmware files. This option is essential because without it, a VoIP phone would not know where to retrieve its provisioning settings, making it unable to register with a call manager. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of DHCP options in enterprise networks, often appearing in troubleshooting scenarios where phones fail to boot or download configurations. A common trap is confusing option 150 with option 66, which also specifies a TFTP server but uses a hostname rather than an IP address—option 150 is the Cisco-proprietary method for IP phones. Memory tip: think “150 = one TFTP server IP” for phones, while “66 = six-character hostname” for generic devices.
300-410 DHCP (IPv4 and IPv6) Practice Question
This 300-410 practice question tests your understanding of dhcp (ipv4 and ipv6). This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Router R5 has this DHCP configuration:
ip dhcp pool POOL3
network 172.16.0.0 255.255.255.0
default-router 172.16.0.1
option 150 ip 10.10.10.10
!
interface GigabitEthernet0/0
ip address 172.16.0.1 255.255.255.0
no shutdown
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It provides the IP address of a TFTP server to DHCP clients, typically used by VoIP phones.
Option 150 is a DHCP option that specifies the IP address of a TFTP server. Cisco IP phones use this option to locate the TFTP server from which they download their configuration and firmware files. The correct answer is A because this is the standard purpose of option 150 in a Cisco VoIP environment.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
It provides the IP address of a TFTP server to DHCP clients, typically used by VoIP phones.
Why this is correct
Option 150 is used to specify a TFTP server for VoIP phones or other devices that need to download configuration files.
Related concept
Read the scenario before looking for a memorised answer.
✗
It sets the DNS server for the DHCP pool.
Why it's wrong here
DNS server is set with the dns-server command, not option 150.
✗
It defines a custom option that is ignored by standard DHCP clients.
Why it's wrong here
Option 150 is a well-known option for TFTP server; it is not ignored by devices that support it.
✗
It specifies the default gateway for the clients.
Why it's wrong here
The default gateway is set with the default-router command, not option 150.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse option 150 with option 66 (TFTP server name) or assume it is a generic custom option, but Cisco specifically tests that option 150 provides the TFTP server IP address for VoIP phones.
Trap categories for this question
Command / output trap
DNS server is set with the dns-server command, not option 150.
Detailed technical explanation
How to think about this question
DHCP option 150 is a Cisco-proprietary option that carries a single IP address or a list of IP addresses for TFTP servers. When a Cisco IP phone boots, it sends a DHCP discover with option 60 (Vendor Class Identifier) set to 'Cisco IP Phone', and the DHCP server responds with option 150. This allows the phone to automatically discover the TFTP server without manual configuration. In contrast, RFC 2132 defines option 66 for TFTP server name, but Cisco uses option 150 for IP address-based TFTP server assignment.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 300-410 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
DHCP (IPv4 and IPv6) — This question tests DHCP (IPv4 and IPv6) — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: It provides the IP address of a TFTP server to DHCP clients, typically used by VoIP phones. — Option 150 is a DHCP option that specifies the IP address of a TFTP server. Cisco IP phones use this option to locate the TFTP server from which they download their configuration and firmware files. The correct answer is A because this is the standard purpose of option 150 in a Cisco VoIP environment.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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