[one-users] instance running with IP but can't ping

[song]

Hi there:

    I use sunstone to create Virtual network and Template,more details 
listed below:

=======================================================
      virtual network:
          Name : net1
          Mode : default
          Bridge:br0(I have a bridge on host named br0)
           Network : fixed  192.168.0.180~192.168.0.200
    and I added the Gateway and DNS

*************************************************************************
     templates:
     CONTEXT=[
   ETH0_DNS="$NETWORK[DNS, NETWORK=\"net1\"]",
   ETH0_GATEWAY="$NETWORK[GATEWAY, NETWORK=\"net1\"]",
   ETH0_IP="$NIC[IP, NETWORK=\"net1\"]",
   ETH0_MASK="$NETWORK[NETWORK_MASK, NETWORK=\"net1\"]",
   ETH0_NETWORK="$NETWORK[NETWORK_ADDRESS, NETWORK=\"net1\"]" ]
CPU="1"
MEMORY="512"
NAME="template1"
NIC=[
   NETWORK="net1",
   NETWORK_UNAME="oneadmin" ]
OS=[
   ARCH="x86_64",
   BOOT="hd" ]
RAW=[
   TYPE="kvm" ]
TEMPLATE_ID="46"
===============================================

After doing all of this ,I run a instance with image from marketplace 
named virtual router,instance startup with image from marketplace too 
named ubuntu 12.04  running with an expected Ip 192.168.0.180,but I 
can't ping it.I wanna to know why and how can I make it work?

Thanks for your reading!