Hi Tejas, “DNS server is currently hosted in public network subnet which is being used by all the tenants”.
Is this DNS server hosted directly on the public network and externally to CloudStack, or is it hosted on a CloudStack isolated/VPC network with DNS services port forwarded to the public network? If the latter then we have seen a few issues around “hairpin NATing” – where VMs on one isolated network isn’t able to access services on another isolated network over the common public network. This has been found to be down to order of Iptables rules on the VR. There were a few PRs to fix this issue earlier in the summer – and I believe those fixes have been included in 4.9.3. If the former – i.e. you are simply hosting a DNS server directly on the public network then I haven’t seen this before, I would suggest doing some packet sniffing to see what is going on on the network. A couple of obvious ones which you have probably checked: - Is the VR actually handing out the correct DNS settings to the clients? If not it could be the DNSmasq DHCP service is unhappy about something. - Any reason why you aren’t just letting the clients use the VR for DNS forwarding, rather than going direct? Regards, Dag Sonstebo Cloud Architect ShapeBlue On 06/10/2017, 09:37, "Tejas Sheth" <tshet...@gmail.com> wrote: Hello, We started facing strange issue with cloudstack VM. where all the VMs in one particular tenant are not able to resolve DNS. since we are using advanced networking we have tried to reboot virtual router and other DNS services. still that particular tenant is not able to resolve the DNS. following troubleshooting steps completed. 1) From the tenant (with issue) we are able reach DNS server with ICMP (ping) 2) from other tenant we are able to reach DNS server on ICMP. also DNS resolution working from other tenant. 3) We have checked ingress and egress traffic settings where we have allowed all inbound and outbound but still DNS resolution is not working. NOTE: DNS server is currently hosted in public network subnet which is being used by all the tenants dag.sonst...@shapeblue.com www.shapeblue.com 53 Chandos Place, Covent Garden, London WC2N 4HSUK @shapeblue