find IP and MAC addresses allocated by neutron dnsmasq-dhcp server

1)
# ip netns
qdhcp-f6e86850-32e9-4366-a03b-2b2a9ac481f0

2)
# ip netns exec qdhcp-f6e86850-32e9-4366-a03b-2b2a9ac481f0 ifconfig

tapbe2e899a-38 Link encap:Ethernet  HWaddr fb:14:3e:41:56:c1

3)
# ip netns exec qdhcp-f6e86850-32e9-4366-a03b-2b2a9ac481f0 arp-scan --interface tapbe2e899a-38 10.140.15.255/24