[ovirt-users] network problem in ovirt3.6.1

hi everyone i dont know why some guests have network problem. for example my guest can ping the host but host cant ping the guest. but when guest ping the host and host can ping guest too ! i attach the hypervisor vdsm log. my ip addr command show that interfaces that related to guest is down or unknown state. 18: vnet1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master Du state UNKNOWN qlen 500 link/ether fe:1a:4a 23: vnet0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master USD state UNKNOWN qlen 500 link/ether fe:1a:4a 26: vnet2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master USD state UNKNOWN qlen 500 link/ether fe:1a:4a:16:01:57 brd ff:ff:ff:ff:ff:ff 30: ovirtmgmt: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP link/ether a0:b3:cc inet 192.168.6.7/24 brd 192.168.6.255 scope global ovirtmgmt valid_lft forever preferred_lft forever