Randomly Changing IP Address


I’m experiencing a very bizarre problem. I have a QNX machine with 6 Ethernet ports. I set the Ethernet ports in my rc.local file. After some time elapses, the IP address will change without warning. I shouldn’t say that it chooses a random IP address, as it seems to like, but it sometimes chooses a different value. This intermittent problem has been causing me a lot of grief and I’d appreciate any suggestions for debugging this issue.

I also have 3 other QNX machines configured identically, but I’m only experiencing this problem with one of the machines. Is there anything I can do besides reinstall QNX on the problematic machine?


Are you using DHCP?

No DHCP. I set it to configure the IP addresses manually. The IP address doesn’t even necessarily change within a couple minutes of boot up, sometimes it takes hours.

This is very strange. The only way I know of to change the IP address manually is with ifconfig. It might be interesting to boot up, and temporarily disable ifconfig, say by changing its name, and then see if the problem still happens. If this doesn’t tell you something, there are two places to look. 1) The TCP/IP manager is undergoing a flaky bug. This is unlikely, especially as you don’t see it anywhere else. 2) Some process is sending a message, either intentionally or accidentaly that tells the manager to change the IP. I would boot up your system, minimally, and see if this still happens. Don’t start anything but OS processes, TCP/IP, and shells. Then wait. I’d also disconnect the system from the network in case it is incoming traffic causing the problem. If the problem goes away, add items one at a time to see what causes the problem.