220-1101 Networking Practice Question
A technician configures a new workstation on a managed switch port. The workstation successfully obtains an IP address from the DHCP server and can ping its own IP address as well as the default gateway. However, it cannot ping any other workstations on the same subnet. The technician has verified that the Ethernet cable is good and the switch port link is up. Which of the following should the technician check NEXT?
⚠ Common exam trap
CompTIA often tests the concept that DHCP and gateway connectivity can work across a router or Layer 3 switch even if the workstation is in a different VLAN, tricking candidates into thinking Layer 3 is fine and ignoring the Layer 2 segmentation caused by VLAN misconfiguration.
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 VLAN assignment on the switch port
The workstation can obtain an IP address and ping the default gateway, indicating Layer 3 connectivity to the local subnet is functional. The inability to ping other workstations on the same subnet suggests a Layer 2 isolation issue, most commonly caused by the switch port being assigned to a different VLAN than the other workstations. VLANs segment broadcast domains, so devices in different VLANs cannot communicate directly without a router, even if they share the same IP subnet.
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 DNS server settings
Why it's wrong here
DNS resolves hostnames to IP addresses; it has no role in raw IP-level connectivity. Because the technician can successfully ping the default gateway by its IP address, the workstation's TCP/IP stack has valid network connectivity and addressing. Any name-resolution failure would produce a 'host not found' error, not a total inability to ping other workstations by IP. Thus, DNS server settings are irrelevant to this symptom.
- ✗
The workstation's subnet mask
Why it's wrong here
If the subnet mask were incorrect, the workstation would likely fail to ping the gateway or obtain a proper IP. It obtained an IP and can ping the gateway, so the subnet mask is almost certainly correct.
- ✓
The VLAN assignment on the switch port
Why this is correct
If the switch port is assigned to a different VLAN than the other workstations, the workstation will be isolated despite being on the same IP subnet. This would allow communication with the gateway (if it routes between VLANs) but not with other hosts in the same IP range that are in a different VLAN.
- ✗
The speed and duplex settings on the switch port
Why it's wrong here
Speed and duplex mismatches cause symptoms like excessive CRC errors, late collisions, severe throughput degradation, or flapping link status. Such conditions rarely prevent all ICMP echo traffic, especially a simple ping to a nearby gateway, and would more likely manifest as timeouts or high latency under load. If the workstation can ping the gateway but not other workstations in the same IP range, a Layer 2 segregation issue like an incorrect VLAN exceeds the likelihood of a duplex misconfiguration. Therefore, speed/duplex settings are not the primary cause of this complete isolation.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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