bridge network ping problem

[嘉谟]

I use tap mode for the guest  network in qemu .

here is /etc/sysconfig/network-scripts/ifcfg-br0


  2 DEVICE=br0
  3 TYPE=Bridge
  4 BOOTPROTO=static
  5 ONBOOT=yes
  6 DNS1=192.168.1.1
  7 GATEWAY=10.16.255.254
  8 IPADDR=10.16.172.77
  9 NETMASK=255.255.0.0
 10 ONBOOT=yes
 11 DELAY=0
 12 STP=off
(line number)

 /etc/sysconfig/network-scripts/ifcfg-em1


  1 DEVICE="em1"
  2 ONBOOT=yes
  3 HWADDR=
  4 NM_CONTROLLED="no"
  5 TYPE=Ethernet
  6 PREFIX=24
  7 DEFROUTE=yes
  8 IPV4_FAILURE_FATAL=yes
  9 IPV6INIT=no
 10 NAME="System em1"
 11 UUID=1dad842d-1912-ef5a-a43a-bc238fb267e7
 12 BRIDGE=br0


use a sh script to biuld tap


  3 tunctl -t tap0 -u root
  4 brctl addif br0 tap0
  5 ifconfig tap0 up
  6 ifconfig tap0 0.0.0.0 promisc up


 qemu use  like  -net nic -net tap

Make guest os

ip 10.16.172.18
netmask:255.255.0.0
gateway:10.16.255.254
dns: 192.168.1.1


Here is i got problem .
guest ping www.google.com is ok
but host os ping 10.16.172.78 get error:

PING 10.1.172.78 (10.1.172.78) 56(84) bytes of data.