CompTIA A+ Core 1 (220-1201)NetworkingHard
A technician installs a new NIC driver and wants to verify that the local TCP/IP stack is functioning correctly before testing connectivity to the network. Which IP address should the technician ping to test this?
- A0.0.0.0
- B169.254.1.1
- C127.0.0.1
- D255.255.255.255
Show answer & explanationAnswer & explanation
Correct answer: C. 127.0.0.1
127.0.0.1 is the IPv4 loopback address, reserved to test a device's own TCP/IP stack without sending traffic onto the physical network. A successful ping confirms the stack is functioning independent of the NIC's link status.
Why the other options are wrong
- A. 0.0.0.0 represents an unspecified/default route address, not used for loopback testing.
- B. 169.254.1.1 is within the APIPA range, indicating a failed DHCP assignment, not a loopback test.
- D. 255.255.255.255 is the limited broadcast address, sent to all hosts on the local segment.
Loopback Address (127.0.0.1)
A reserved IPv4 address used to test a device's own network stack without requiring physical network connectivity.
- Entire 127.0.0.0/8 range is reserved for loopback
- IPv6 equivalent is ::1
- Successful ping confirms TCP/IP stack works regardless of NIC/cable status
Memory trick: '127, look in the mirror' — pinging yourself.