In a variety of books and learning materials, we're told that if pinging the localhost/loopback address fails, this is a sign of a malfunctioning TCP/IP stack. What we aren't told is why/how this may happen. I've searched and found ways in rebuilding the stack, but haven't been able to find why a TCP/IP stack would fail if it had been functional previously, and I've personally never had a failure, and rarely see problems relating to a failed stack. Obviously the latter is subjective, but I mean more so in a general sense; help boards, technical issues discussed, etc.

1 Answer 1


I'm not sure why you included the phrase "if it had been functional previously". Does that really relate to the learning materials you mention?

If you omit that phrase -- yes, I've seen malfunctionaing TCP/IP stacks. After all, they consist of several layers, each of which must be correctly registered with the operating system.

If you don't omit that phrase -- you can still imagine changing BIOS settings, or an additional driver must be loaded such that the kernel runs out of resources (semaphores, memory pools, ...) required for the new configuration, due to inconsistent settings.

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    The "...if it had been functioning previously...", was more so to better understand how and why the TCP/IP stack can fail/no longer work.
    – Hammy
    Commented Dec 18, 2015 at 20:29

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