Question 986 of 972
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220-1201 Practice Question: A technician is configuring a router with two…
A technician is configuring a router with two interfaces: WAN (DHCP from ISP) and LAN (static IP 10.0.0.1/24). The technician sets the LAN subnet mask to 255.255.255.0. A workstation is assigned IP 10.0.0.100/24 and can ping the router, but cannot access the internet. The router's WAN interface has IP 203.0.113.5/30. What is the most likely missing configuration?
⚠ Common exam trap
The 220-1201 exam often tests the misconception that a workstation being able to ping the router's LAN interface implies full internet connectivity, when in fact the router itself lacks a route to forward traffic beyond its directly connected networks.
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
✓
The router lacks a default route pointing to the ISP's gateway.
The workstation can ping the router's LAN interface (10.0.0.1), confirming Layer 2 and basic IP connectivity on the LAN. However, for the workstation to reach the internet, the router must have a default route (0.0.0.0/0) pointing to the ISP's next-hop gateway (likely 203.0.113.6, the other end of the /30 WAN link). Without this route, the router does not know where to forward packets destined for external networks, even though the WAN interface has a valid IP from DHCP.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The workstation's default gateway is set to 10.0.0.1.
Why it's wrong here
This option is incorrect because the problem statement implies the workstation can reach the router but not the internet. If the workstation can successfully ping its default gateway (the router at 10.0.0.1), it confirms that the workstation's default gateway setting is correctly configured. Therefore, the workstation's ability to communicate with the router indicates this specific setting is not the cause of the broader internet connectivity issue.
- ✓
The router lacks a default route pointing to the ISP's gateway.
Why this is correct
This is the correct answer. A router requires a default route, typically configured as 0.0.0.0/0, to direct all traffic for networks not explicitly defined in its routing table. Without this crucial entry, the router cannot determine the next hop for external internet-bound traffic, even if its WAN interface has a valid IP address and can communicate with the ISP's gateway. Consequently, devices on the LAN would be unable to access the internet.
- ✗
The WAN subnet mask should be 255.255.255.0.
Why it's wrong here
This option is incorrect. ISPs commonly assign a /30 subnet mask (255.255.255.252) for point-to-point WAN links between the customer router and the ISP's gateway. This efficient allocation provides just enough IP addresses for the two endpoints. Changing it to a /24 (255.255.255.0) would incorrectly expand the subnet, potentially causing IP address conflicts or preventing proper communication with the ISP's gateway, thus breaking WAN connectivity rather than fixing it.
- ✗
The LAN subnet mask should be 255.255.0.0.
Why it's wrong here
This option is incorrect. A /24 subnet mask (255.255.255.0) is a standard and appropriate choice for most small to medium-sized LANs, providing 254 usable host IP addresses. Changing it to a /16 (255.255.0.0) would significantly expand the local network's address space, which is unnecessary and could introduce broadcast domain issues without resolving the fundamental problem of internet access. The existing /24 mask allows local communication and is not the cause of the internet connectivity failure.
Visual reference
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Last reviewed: Jul 4, 2026
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