[libvirt] Question about virbr(dnsmasq)

[Nobuhiro Itou <fj0873gn aa jp fujitsu com>]

Hi all.

I have the question about the option of dnsmasq that libvirt sets as a default virtual network.
Why does dnsmasq listen to all NICs as specified "--except-interface lo"?


And, at the following conditions, the message is output to /var/log/messages. 
Do you know why it is output?

Conditions:
  1) Dnsmasq is started by libvirt. And...
     # ps -ef | grep dnsmasq
     nobody    5877  5754  0 Jul30 ?        00:00:00 /usr/sbin/dnsmasq --keep-in-foreground --strict-order 
     --bind-interfaces --pid-file  --conf-file  --listen-address 192.168.122.1 --except-interface lo 
     --dhcp-leasefile=/var/lib/libvirt/dhcp-default.leases --dhcp-range 192.168.122.2,192.168.122.254
  2) chenge the network address to '0.0.0.0'. And...
     # ifconfig eth3 0 up
  3) Dnsmasq recieves DHCPINFORM message from other DHCP servers.
Message:
  dnsmasq[5877]: no address range available for DHCP request via eth3


Thank you
Nobuhiro Itou