Comment 1 for bug 1715734

Instead of setting a source why aren't you using the -U flag? It's missing from that command line.

This:
arping_cmd = ['arping', arg, '-I', iface_name, '-c', 1,
              # Pass -w to set timeout to ensure exit if interface
              # removed while running
              '-w', 1.5, address]

Does not generate a gratuitous ARP.