Networking Fundamentals Practice Question 8: DHCP Link Local Fallback
Networking Fundamentals · Test 1 · question 8 of 10
A user's desktop is set to obtain an IP address automatically. It can't reach any websites or file shares, and ipconfig shows the address 169.254.37.12 with mask 255.255.0.0 and no default gateway. What does this most likely indicate?
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Answer:
169.254.0.0/16 is the IPv4 link-local block. When no other configuration is available, typically because no DHCP server answered, a host can pick an address from this block by itself. On Windows this is called APIPA. Link-local addresses aren't routable and come with no gateway, so the machine can reach at most other link-local hosts on the same segment. So C is correct. Next, check the cable or Wi-Fi association, the switch port or VLAN, and whether the DHCP server (or the DHCP relay on the router) is working.
- A. A DNS failure breaks name resolution but doesn't change the machine's address. A host with a DHCP lease would still show its normal address and gateway. - B. An address conflict is reported as a duplicate-address error. It doesn't produce a 169.254.x.x address with no gateway configured. - D. 169.254/16 is not an RFC 1918 private range, and a properly working DHCP server does not hand out link-local addresses. Its absence explains the address better than a misconfiguration.
Reference: RFC 3927 - Dynamic Configuration of IPv4 Link-Local Addresses, section 1