thanks for your reply!
I have plugged the tap0 to the bridge.
when I create the tap0:

tunctl -t tap0 -u root

brctl addif br0 tap0

ifconfig tap0 up

chmod a+rw /dev/net/tun

echo 1 > /proc/sys/net/ipv4/ip_forward

iptables -t nat -A POSTROUTING -j MASQUERADE


so I think this is not the reason.


wh.h@foxmail.com
 
From: Michal Privoznik
Date: 2015-04-20 18:09
To: wh.h@foxmail.com; libvirt-users
Subject: Re: [libvirt-users] inquiry about differences between the tap and the vnet in the virt-manager
On 19.04.2015 04:02, wh.h@foxmail.com wrote:
> inquiry about differences between the tap and the vnet in the virt-manager
>
 
> when I establish the network by the first method: create a bridge with the help of Linux commad: brctl, tap0 device is created in the host and assigned to the guest OS. tap0 device gets a name “eth0” in the guest OS.
> I use “ping ” command to test network state . I get the following result :
> concept explanation :
> local host: the OS where the guest OS is running
> remote host: another server which is connected to the local host using ethernet network .
> and this is my results:
> ping local host from guest OS is OK, I get reply from local host;
> ping remote host from local host is OK, I get reply from remote host;
> ping remote host from guest OS is not OK, I don’t get any reply from remote host; and this is my question.
 
Do you plug the tap0 into the bridge? This could be the missing piece.
 
Michal