i construct nodes (juno-,packstack , centos7, 3node- contoroller, compute, network+compute)

Problem is... when i execute yum update in vm that locate compute node. network+compute node is down, network is disconnect and soon(maybe 5minute later) recover connection... this phenomenon repeat two-three times.

but vms in network+compute are fine when i execute yum update. even vms in compute has no error to connect external network(like ssh , ping....)

gre, vxlan has same phenomenon... please help