CCNA Network Services and Security Practice Question
A branch office uses PAT for user Internet access. The administrator notices that inside users can browse out, but an internal server still cannot be reached consistently from outside. Which change is most appropriate?
⚠ Common exam trap
A frequent exam trap is to confuse the role of PAT and static NAT, leading to the incorrect assumption that disabling NAT or changing VLANs will fix inbound server reachability. Disabling NAT entirely stops all address translation, breaking Internet access for all internal hosts. Changing VLANs, such as moving a server to the native VLAN, does not affect NAT or public accessibility. Another trap is to replace PAT with unrelated features like DHCP relay, which does not influence NAT or inbound connections. Understanding that static NAT is required for stable inbound access while PAT supports outbound user traffic avoids these mistakes.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add a static NAT mapping for the server while leaving PAT in place for user traffic.
The most appropriate change is to add a static NAT mapping for the internal server while keeping PAT for ordinary user traffic. In practical terms, PAT solves the many-users-outbound problem by allowing shared use of a public address. But an inbound-published server needs a stable, predictable public identity. That requirement is different from the requirement for user browsing. This is a common NAT design distinction. PAT and static NAT can coexist because they solve different problems. The best answer is the one that preserves PAT for users while giving the server a fixed public translation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Add a static NAT mapping for the server while leaving PAT in place for user traffic.
Why this is correct
A static NAT mapping binds the server's private IPv4 address to a specific public IPv4 address, creating a permanent inside-global entry that lets Internet clients initiate connections to the server. At the same time, PAT overload remains in place for user traffic, translating many internal addresses to one public IP and tracking flows by source port. This hybrid design preserves outbound Internet access while giving the server a stable, globally reachable identity without disabling translation.
- ✗
Replace PAT with DHCP relay.
Why it's wrong here
DHCP relay is an IP helper mechanism that forwards DHCPDISCOVER broadcasts between subnets so clients in one VLAN can obtain leases from a DHCP server in another subnet. It performs no address translation and creates no public-to-private mapping, so it cannot provide Internet reachability for the server. Replacing PAT with DHCP relay would eliminate the only translation mechanism in use, making the server even less reachable from the Internet.
When this WOULD be correct
In a scenario where a question asks about optimizing a network for dynamic IP address allocation and the need for clients to communicate with a DHCP server located on a different subnet, replacing PAT with DHCP relay could be the correct answer, as it would facilitate the proper forwarding of DHCP requests.
- ✗
Disable NAT entirely because PAT is preventing inbound routing.
Why it's wrong here
Disabling NAT entirely would remove the translation that maps the branch's private RFC1918 addresses to routable public addresses, causing user packets to be dropped by the ISP because private addresses are not routable on the Internet. PAT itself does not prevent inbound routing; it simply lacks a translation entry for unsolicited packets destined to the server, which is why an inbound connection fails. The correct remedy is to add a static NAT mapping, not to turn off NAT altogether.
When this WOULD be correct
In a different scenario where a network is experiencing severe routing issues due to misconfigured NAT settings, disabling NAT might be the correct solution to restore connectivity and allow for proper routing of traffic to and from the internal network.
- ✗
Put the server in the native VLAN.
Why it's wrong here
Placing the server in the native VLAN changes only the Layer 2 domain for untagged frames on a trunk, typically used for management or specific legacy traffic. This action has no effect on Layer 3 address translation and does not create any public mapping, so Internet clients still cannot reach the server. The native VLAN is unrelated to NAT/PAT and cannot publish a server to the public Internet.
When this WOULD be correct
In a different scenario where the question asks about optimizing internal traffic flow and VLAN configurations, placing a server in the native VLAN could be correct if the goal is to simplify access for internal users without needing additional NAT configurations.
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.
✓Add a static NAT mapping for the server while leaving PAT in place for user traffic.Correct answer▾
Why this is correct
A static NAT mapping binds the server's private IPv4 address to a specific public IPv4 address, creating a permanent inside-global entry that lets Internet clients initiate connections to the server. At the same time, PAT overload remains in place for user traffic, translating many internal addresses to one public IP and tracking flows by source port. This hybrid design preserves outbound Internet access while giving the server a stable, globally reachable identity without disabling translation.
✗Replace PAT with DHCP relay.Wrong answer — click to see why▾
Why this is wrong here
Replacing PAT with DHCP relay does not address the issue of inbound access to the internal server; DHCP relay is used for forwarding DHCP requests, not for managing NAT or routing traffic to servers.
★ When this WOULD be the correct answer
In a scenario where a question asks about optimizing a network for dynamic IP address allocation and the need for clients to communicate with a DHCP server located on a different subnet, replacing PAT with DHCP relay could be the correct answer, as it would facilitate the proper forwarding of DHCP requests.
Why candidates choose this
Candidates may confuse the need for inbound access with the configuration of IP address management, leading them to believe that changing NAT methods could resolve connectivity issues related to server access.
✗Disable NAT entirely because PAT is preventing inbound routing.Wrong answer — click to see why▾
Why this is wrong here
Disabling NAT entirely would prevent all internal users from accessing the Internet, which is not the desired outcome in this scenario. The issue is with inbound traffic to the server, not with NAT itself.
★ When this WOULD be the correct answer
In a different scenario where a network is experiencing severe routing issues due to misconfigured NAT settings, disabling NAT might be the correct solution to restore connectivity and allow for proper routing of traffic to and from the internal network.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of how NAT functions, believing that disabling it will solve all routing issues, rather than recognizing that specific NAT configurations can be adjusted to allow for inbound traffic.
✗Put the server in the native VLAN.Wrong answer — click to see why▾
Why this is wrong here
Putting the server in the native VLAN does not address the issue of inconsistent external access, as it does not resolve the NAT configuration required for inbound traffic to reach the server. The server still needs a proper NAT mapping to be accessible from outside the network.
★ When this WOULD be the correct answer
In a different scenario where the question asks about optimizing internal traffic flow and VLAN configurations, placing a server in the native VLAN could be correct if the goal is to simplify access for internal users without needing additional NAT configurations.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of VLANs and their role in network segmentation, mistakenly believing that changing VLAN settings could resolve NAT-related access issues.
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?”
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Key term
CAN
A CAN (Controller Area Network) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other without a host computer.
Key term
NAT
NAT (Network Address Translation) is a method that allows multiple devices on a private network to share a single public IP address when accessing the internet.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.