prevent_arp_spoofing in liberty prevents applications

[ioannis]

In Liberty the default option is: prevent_arp_spoofing = True
If a VM is configured with subnet mask different to /24, e.g. a /20, then if an application is listening to same subnet (but not if it was /24), it won't reply to arp requests.

For example,
VM A interface is 10.1.2.3/20 and there is an application listening to 10.1.3.4 on the same VM.
VM B interface is 10.1.2.4/20.

If you ping 10.1.3.4 from VM B, neutron will not forward arp reply to VM B. So, even if both A and B are on the same subnet, they cannot exchange arp requests, so they cannot connect to applications running.
Ping works if you ping from VM B the VM A in 10.1.2.3.

[Brian Haley (brian-haley)]

Please re-open if this is still an issue, but provide more information on how you reproduced this.