CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. 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. A key principle to apply: cisco routers allow configuration of VTY lines to specify which remote management protocols are accepted, such as SSH or Telnet.. 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.
An administrator wants to block all Telnet access to a router’s VTY lines and allow only SSH. Which change most directly supports that goal?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the VTY lines to accept SSH and not Telnet.
The most direct change is to configure the VTY lines to accept only SSH, which removes Telnet as an accepted protocol. Option B (PortFast) is a spanning-tree feature that speeds up port transition on access ports and has nothing to do with VTY access. Option C (DHCP snooping) is a Layer 2 security feature to prevent rogue DHCP servers; it does not affect VTY line protocols. Option D (OSPF hello interval) is an OSPF timer adjustment, unrelated to remote access security. Therefore, only option A directly achieves the goal.
Key principle: Cisco routers allow configuration of VTY lines to specify which remote management protocols are accepted, such as SSH or Telnet.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Configure the VTY lines to accept SSH and not Telnet.
Why this is correct
This is correct because it directly restricts the management protocol accepted on the router.
Related concept
Cisco routers allow configuration of VTY lines to specify which remote management protocols are accepted, such as SSH or Telnet.
✗
Enable PortFast on the VTY lines.
Why it's wrong here
This is wrong because PortFast is a switching feature, not a router management-line control.
When this WOULD be correct
If the question were about optimizing switch port configurations for rapid connectivity in a network where VTY lines are used for management, then enabling PortFast could be the correct answer. For example, a question might ask how to reduce the time it takes for a switch port to become active after being connected.
✗
Use DHCP snooping to protect the VTY lines.
Why it's wrong here
This is wrong because DHCP snooping is unrelated to router management transport protocols.
When this WOULD be correct
If the question were about securing a network against unauthorized DHCP servers affecting devices that connect to the router, then using DHCP snooping would be the correct answer. In that scenario, the focus would be on protecting the network's IP address assignment rather than access protocols like Telnet or SSH.
✗
Increase the OSPF hello interval.
Why it's wrong here
This is wrong because OSPF timer changes do not secure VTY access.
When this WOULD be correct
If the question asked about optimizing OSPF performance in a network where OSPF is being used, increasing the hello interval could be correct. For instance, a scenario might involve reducing OSPF traffic in a stable network environment.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Configure the VTY lines to accept SSH and not Telnet.Correct answer▾
Why this is correct
This is correct because it directly restricts the management protocol accepted on the router.
✗Enable PortFast on the VTY lines.Wrong answer — click to see why▾
Why this is wrong here
PortFast is a Cisco switch feature used to immediately transition an access port to the forwarding state, bypassing Spanning Tree Protocol convergence. It has no relevance to router VTY lines or management access protocols.
★ When this WOULD be the correct answer
If the question were about optimizing switch port configurations for rapid connectivity in a network where VTY lines are used for management, then enabling PortFast could be the correct answer. For example, a question might ask how to reduce the time it takes for a switch port to become active after being connected.
Why candidates choose this
A student might confuse PortFast with a feature that speeds up or secures connections, but it is unrelated to VTY line configuration and is only applicable to switch ports.
✗Use DHCP snooping to protect the VTY lines.Wrong answer — click to see why▾
Why this is wrong here
DHCP snooping is a security feature on switches that filters untrusted DHCP messages to prevent rogue DHCP servers. It does not affect VTY line access or the transport protocols (Telnet/SSH) used for router management.
★ When this WOULD be the correct answer
If the question were about securing a network against unauthorized DHCP servers affecting devices that connect to the router, then using DHCP snooping would be the correct answer. In that scenario, the focus would be on protecting the network's IP address assignment rather than access protocols like Telnet or SSH.
Why candidates choose this
The term 'snooping' might imply monitoring or blocking, leading a student to think it could restrict Telnet, but DHCP snooping is specifically for DHCP traffic and not for management protocols.
✗Increase the OSPF hello interval.Wrong answer — click to see why▾
Why this is wrong here
The OSPF hello interval is a timer used in OSPF routing protocol to maintain neighbor relationships. Changing it has no impact on VTY line access or the ability to use Telnet versus SSH for management.
★ When this WOULD be the correct answer
If the question asked about optimizing OSPF performance in a network where OSPF is being used, increasing the hello interval could be correct. For instance, a scenario might involve reducing OSPF traffic in a stable network environment.
Why candidates choose this
A student might think that increasing the hello interval could slow down or block Telnet sessions, but OSPF timers are unrelated to VTY line configuration and do not affect management access.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Avoid assuming that ACLs or global commands can replace specific VTY line configurations for protocol restriction.
Detailed technical explanation
How to think about this question
Virtual Terminal (VTY) lines on Cisco routers provide remote access for device management, typically via Telnet or SSH protocols. Telnet is an older protocol that sends all data, including passwords, in plaintext, making it susceptible to interception and unauthorized access. SSH (Secure Shell), by contrast, encrypts all transmitted data, providing confidentiality and integrity for remote management sessions. Cisco IOS allows administrators to configure which protocols are accepted on VTY lines using the 'transport input' command, enabling precise control over remote access methods.
To block Telnet and allow only SSH, the administrator configures the VTY lines with the command 'transport input ssh'. This setting ensures that the router accepts only SSH connections on its management interfaces, effectively disabling Telnet access. This approach is more secure and direct than relying on external network devices or access control lists to filter Telnet traffic. It enforces security at the management plane level, reducing the attack surface and preventing insecure protocols from reaching the router.
A common exam trap is confusing unrelated features with VTY line security. For example, enabling PortFast affects switch port behavior in Spanning Tree Protocol and does not restrict remote access protocols. Similarly, DHCP snooping protects against rogue DHCP servers but does not control VTY access. Adjusting OSPF hello intervals influences routing protocol operations but has no effect on management protocol restrictions. Understanding the specific role of each feature prevents selecting incorrect answers that do not address the core security requirement of blocking Telnet on VTY lines.
KKey Concepts to Remember
Cisco routers allow configuration of VTY lines to specify which remote management protocols are accepted, such as SSH or Telnet.
Configuring VTY lines to accept only SSH blocks insecure Telnet access, enhancing router management security by enforcing encrypted sessions.
Telnet transmits data in clear text, making it vulnerable to interception, whereas SSH encrypts management traffic to protect credentials and commands.
The 'transport input' command on VTY lines controls which protocols are permitted for remote access, directly impacting router management plane security.
Network administrators should disable insecure protocols like Telnet on management interfaces rather than relying solely on external filtering or ACLs.
PortFast is a Spanning Tree Protocol feature that affects switch port behavior and does not influence router VTY line access control.
DHCP snooping protects against rogue DHCP servers and does not control or restrict router management protocol access on VTY lines.
Changing OSPF hello intervals affects routing protocol timing and convergence but does not impact remote management access methods on routers.
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
Cisco routers allow configuration of VTY lines to specify which remote management protocols are accepted, such as SSH or Telnet.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review cisco routers allow configuration of VTY lines to specify which remote management protocols are accepted, such as SSH or Telnet., then practise related 200-301 questions on the same topic to reinforce the concept.
Network Services and Security — This question tests Network Services and Security — Cisco routers allow configuration of VTY lines to specify which remote management protocols are accepted, such as SSH or Telnet..
What is the correct answer to this question?
The correct answer is: Configure the VTY lines to accept SSH and not Telnet. — The most direct change is to configure the VTY lines to accept only SSH, which removes Telnet as an accepted protocol. Option B (PortFast) is a spanning-tree feature that speeds up port transition on access ports and has nothing to do with VTY access. Option C (DHCP snooping) is a Layer 2 security feature to prevent rogue DHCP servers; it does not affect VTY line protocols. Option D (OSPF hello interval) is an OSPF timer adjustment, unrelated to remote access security. Therefore, only option A directly achieves the goal.
What should I do if I get this 200-301 question wrong?
Review cisco routers allow configuration of VTY lines to specify which remote management protocols are accepted, such as SSH or Telnet., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Cisco routers allow configuration of VTY lines to specify which remote management protocols are accepted, such as SSH or Telnet.
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