Linux server taking unused (and used) IP addresses

I have a Linux server that has started to use IP addresses
on its subnet that are unused or currently not in use.

That is, it is supposed to use X.X.X.13, for example but also
started using X.X.X.10 and .11 which were unused and .14 which
was used by another machine that happened to be turned off
at the time.

This was noticed when .14 was turned back on and could not
connect. This was verified by taking the Linux server off
the network, physically, then pinging these addresses. They
answered the ping.

I am going to quit looking in a few days, save the necessary
data offline then reformat the machine if I cannot resolve
the problem.

Any ideas where to look for answers or to stop this behavior
would be appreciated.

Thanks

ken

(E-Mail Removed) (David Efflandt) wrote in message news:<(E-Mail Removed)>...
> Curious what you mean by "started to use". Do they show up in ifconfig or
> arp -a, and what is output of '/sbin/route -n'? Linux does answer for any
> IP on any of its own interfaces, but should not answer for IPs not on it,
> unless using proxy_arp or bridging. And ping through bridge or
> proxy_arp would fail if those IPs were not online.

The new IP addresses show up in ifconfig, not in arp -a and not in
/sbin/round -n. I have now used ifconfig to delete them and they
seem to be staying off.

>
> > This was noticed when .14 was turned back on and could not
> > connect. This was verified by taking the Linux server off
> > the network, physically, then pinging these addresses. They
> > answered the ping.
>
> Did Linux answer pings for those IPs before you took it offline (did the
> MAC in arp match a Linux interface)? Have you manually assigned any MAC
> addresses that might be conflicting (ie, the same).

I did not manually assign conflicting addresses. I have not changed anything
network configuration related in months.

> Insufficient data. Could be a routing loop or firewall/forwarding
> misconfiguration. I cannot tell you how many times I have seen people
> loop a default route back at themselves.

Thanks so much for your help. I think I may have stopped it but still
don't know how it started. Your information was very helpful.

ken