220-1101 Networking Practice Question
A network technician is troubleshooting a connectivity issue in a small office. A user's computer obtains an IP address starting with 169.254.x.x. The network uses DHCP from a router with IP 192.168.1.1. The technician checks the cable and sees the link light is on. The computer was working yesterday. Which of the following is the most likely cause?
⚠ Common exam trap
Many candidates assume a link light guarantees DHCP functionality, but APIPA indicates DHCP failure at Layer 3, not a physical or data link issue.
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 DHCP server has exhausted its IP pool
The 169.254.x.x address is an Automatic Private IP Addressing (APIPA) address, assigned by Windows when DHCP fails. Since the computer worked yesterday and the link light is on, the most likely cause is that the DHCP server's IP pool is exhausted, preventing new leases. This is a common scenario in small offices with limited IP ranges.
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 DHCP server's IP address changed
Why it's wrong here
If the DHCP server's IP changed, the computer would still attempt to contact the server at the old IP, which would not respond. APIPA would occur, but this is less common than pool exhaustion because DHCP server IP changes are rare and often planned.
When this WOULD be correct
A question where clients previously obtained IPs from a DHCP server but now receive addresses from a different subnet, and the server's IP has changed without updating the DHCP relay or scope configuration.
- ✗
The network cable is a crossover cable
Why it's wrong here
A crossover cable directly connects two similar devices by swapping transmit and receive pairs, but modern network interfaces and switches support Auto-MDI/X, which automatically detects and reconfigures the pinout so that either a straight-through or crossover cable works. Even if a crossover cable were used in this scenario, the link light would still be on and the DHCP exchange would proceed normally, since the physical layer is functional. A crossover cable can only cause a connectivity issue if the hardware lacks Auto-MDI/X, which is rare in modern equipment, and it would not manifest specifically as DHCP failure or APIPA addressing. Therefore, the cable type is not the reason the computer has a 169.254.x.x address.
When this WOULD be correct
A crossover cable would be the correct answer if two computers were directly connected without a switch or router, and the link light was off or the connection failed to establish.
- ✓
The DHCP server has exhausted its IP pool
Why this is correct
The DHCP server's address pool is the finite range of IP addresses it is configured to hand out. Once every address in the scope has been leased to a client, the server can no longer fulfill new lease requests or extend existing leases, so an affected computer fails to obtain a valid IPv4 address. Consequently, the operating system automatically falls back to Automatic Private IP Addressing (APIPA), assigning itself a 169.254.x.x address that cannot route beyond the local subnet. This commonly happens in networks where the number of devices exceeds the available pool or lease times are set too long, and it is a more likely cause than a cable fault because the computer was working previously and the link is still up.
- ✗
The computer's network adapter is faulty
Why it's wrong here
A faulty adapter might cause connectivity issues, but the link light is on and the computer was working yesterday. APIPA is typically a DHCP failure, not a hardware fault. A faulty adapter would likely show other symptoms like no link light or intermittent drops.
When this WOULD be correct
A user's computer cannot obtain an IP address, the link light is off, and other devices on the same switch work fine. In that scenario, a faulty network adapter would be the likely cause.
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 220-1101 exam frequently reuses these exact scenarios with slightly different constraints.
✓The DHCP server has exhausted its IP poolCorrect answer▾
Why this is correct
The DHCP server's address pool is the finite range of IP addresses it is configured to hand out. Once every address in the scope has been leased to a client, the server can no longer fulfill new lease requests or extend existing leases, so an affected computer fails to obtain a valid IPv4 address. Consequently, the operating system automatically falls back to Automatic Private IP Addressing (APIPA), assigning itself a 169.254.x.x address that cannot route beyond the local subnet. This commonly happens in networks where the number of devices exceeds the available pool or lease times are set too long, and it is a more likely cause than a cable fault because the computer was working previously and the link is still up.
✗The DHCP server's IP address changedWrong answer — click to see why▾
Why this is wrong here
The DHCP server's IP address changing would not cause the client to receive a 169.254.x.x address; instead, the client would likely fail to get an IP or get an IP from a different scope, but APIPA only occurs when no DHCP server is reachable.
★ When this WOULD be the correct answer
A question where clients previously obtained IPs from a DHCP server but now receive addresses from a different subnet, and the server's IP has changed without updating the DHCP relay or scope configuration.
Why candidates choose this
Candidates may think that a changed DHCP server IP would prevent clients from reaching it, leading to APIPA, but APIPA is specifically for no response, not a changed server address.
✗The network cable is a crossover cableWrong answer — click to see why▾
Why this is wrong here
A crossover cable would cause no link light or intermittent connectivity, but the link light is on and the computer obtains a 169.254.x.x address, indicating DHCP failure, not a cable issue.
★ When this WOULD be the correct answer
A crossover cable would be the correct answer if two computers were directly connected without a switch or router, and the link light was off or the connection failed to establish.
Why candidates choose this
Candidates may confuse crossover cable symptoms with DHCP issues, thinking a crossover cable could prevent proper network communication, but the link light being on rules out cable faults.
✗The computer's network adapter is faultyWrong answer — click to see why▾
Why this is wrong here
The link light is on, indicating physical connectivity, and the computer was working yesterday, making a sudden adapter failure unlikely. The 169.254.x.x address specifically points to DHCP failure, not hardware fault.
★ When this WOULD be the correct answer
A user's computer cannot obtain an IP address, the link light is off, and other devices on the same switch work fine. In that scenario, a faulty network adapter would be the likely cause.
Why candidates choose this
Candidates may assume any connectivity issue is hardware-related, especially when they see a link light but still have problems, not realizing that link lights only indicate layer 1 connectivity, not DHCP functionality.
Analysis generated from the official 220-1101blueprint 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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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