Please check if you are hit by the “Linux ARP flux” problem. Linux answers ARP requests on wrong and unassociated interfaces per default. This leads to the following two problems:
- ARP requests for the loopback alias address are answered on the HW interfaces (even if NOARP on lo0:1 is set).
- If the machine is connected twice to the same switch (e.g. with eth0 and eth1) eth2 may answer ARP requests for the address on eth1 and vice versa in a race condition manner (confusing almost everthing).
This can be prevented by specific arp kernel settings. Take a look here for additional information about the nature of the problem (and other solutions): http://linux-ip.net/html/ether-arp.html#ether-arp-flux.
To fix that generally (and reboot safe) we recommend to include the following lines into /etc/sysctl.conf:
The following commands may be used to change the settings interactively during runtime:
# echo 1 > /proc/sys/net/ipv4/conf/all/arp_ignore # echo 2 > /proc/sys/net/ipv4/conf/all/arp_announce