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DNS in virtual router not stable


Hi, all, 

We are using Cloudstack 4.9.2 with KVM and advance networking


We are having VPC network, and need to continuously adding / removing VM. 
One issue we found is, from time-to-time, on the VM deployed, it gets 
error that the hostname of the other VM is not resolved.  We dig into the 
VR, and it seems that every time a VM is added or removed, the dnsmasq 
needs to be restarted.  And based on /var/log/dnsmasq.log, there is 2 
second delay before dnsmasq is running again.  Quite likely while restart 
is happening, the DNS is not working and therefore VM will not be able to 
resolve hostname. 

Dec 12 15:22:55 dnsmasq[6479]: exiting on receipt of SIGTERM
Dec 12 15:22:57 dnsmasq[6747]: started, version 2.62 cachesize 150
Dec 12 15:26:36 dnsmasq[6747]: exiting on receipt of SIGTERM
Dec 12 15:26:38 dnsmasq[28921]: started, version 2.62 cachesize 150


We don't see this issue in CloudStack 4.11.  In 4.11, we also see dnsmasq 
being restarted in dnsmasq.log, but there is no delay between exiting and 
started. 

Is there anything we can do in 4.9.2 to have the DNS more stable.  e.g. 
can dnsmasq not being restarted even new VM info is added?  Or can it just 
reload the VM info?


Thanks
Ivan