Description of problem:
I start two vm guests and add three network devices of virtio-net-pci type in each guest using qemu-kvm, then eth0/eth1/eth2 are created in each guest. After that I create a bond interface in each guest using eth1 and eth2, and connect the two guests using a bridge. At last I run ping6 from one guest to another and wait several seconds, then one of guests' IPv6 neighbour information often failed.

# ip -6 neigh show dev bond0
2001:db8:ffff:2::1  FAILED

|------------------|                                 |------------------|
|   eth0           |                                 |            eth0  |
|    |    |--eth1--|--tap_client_1--|--tap_server_1--|--eth1--|    |    |
| client--|--bond0 |              bridge             | bond0--|--server |
|         |--eth2--|--tap_client_2--|--tap_server_2--|--eth2--|         |
|                  |                                 |                  |
|------------------|                                 |------------------|

Version-Release number of selected component (if applicable):
RHEL-6.8-20160414.0 ==> kernel-2.6.32-642.el6


How reproducible:
often (50%?)


Steps to Reproduce:
1. start two vm guests and add at least two network devices in each guest using qemu-kvm. (qemu-kvm command is like this)
# /usr/libexec/qemu-kvm -name server -drive file=/home/server_el6.qcow2,if=none,id=drive-virtio-disk1,media=disk,cache=none,snapshot=off,format=qcow2,aio=native -device virtio-blk-pci,drive=drive-virtio-disk1,id=virtio-disk1,bootindex=0 -netdev tap,id=hostnet0,vhost=on,script=/etc/br_wan_ifup,downscript=/etc/br_wan_ifdn,ifname=tap_server_0 -device virtio-net-pci,netdev=hostnet0,id=virtio-net-pci0,mac=00:7d:73:3c:fe:25 -netdev tap,id=hostnet1,vhost=on,script=/etc/br_lan_ifup,downscript=/etc/br_lan_ifdn,ifname=tap_server_1 -device virtio-net-pci,netdev=hostnet1,id=virtio-net-pci1 -netdev tap,id=hostnet2,vhost=on,script=/etc/br_lan_ifup,downscript=/etc/br_lan_ifdn,ifname=tap_server_2 -device virtio-net-pci,netdev=hostnet2,id=virtio-net-pci2 -serial file:/home/server_el6.console -serial pty -vnc :13 -qmp tcp:0:11313,server,nowait  -smp 2,cores=1,threads=1,sockets=2 -m 4096
2. create a bond interface in each guest using the two network devices
3. connect two vm guests using a bridge
4. run ping6 from one guest to another using bond interfaces


Actual results:
IPv6 neighbour information often failed.


Expected results:
IPv6 neighbour information does not fail.


Additional info:
If I using e1000 device instead of virtio-net-pci when create interface in vm guests, the IPv6 neighbour information is OK.