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Quantum, DNSMasq, and resolv.conf

asked 2013-09-13 22:13:48 -0500

jskains gravatar image

We moved from a FlatDHCP system to a GRE/Quantum based system. Before, the VM's would get a DNS server controlled my dnsmasq, but then dnsmasq would forward the information to the set external DNS servers. In this scheme, each VM would have a resolvable hostname with the local dnsmasq server.

When we moved to Quantum, following the instructions on docs.openstack.org , it seems dnsmasq now passes the external DNS to the VMs, which of course does not have a resolvable address for the VMs, and the VM's hang on different functions with "unable to resolve <hostname>". The /etc/hosts file only has a "localhost" entry and /etc/resolv.conf has just the external DNS in this case being 8.8.8.8..... How do I get Quantum to use dnsmasq for a DNS server that manages VM names and IPs like in the flatDHCP method?</hostname>

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I am seeing the same issue with Neutron in Icehouse. Were you able to get around this issue?

opstkusr gravatar imageopstkusr ( 2014-11-06 13:45:44 -0500 )edit

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answered 2014-12-16 07:13:50 -0500

Zollner Robert gravatar image

At least on havana and icehouse , dhcp neutron agent is preventing dnsmasq to use nameservers from /etc/resolv.conf (using the --no-resolv parameter)

Default behaivior of the dhcp agent is to advertise itself as the dns server to the virtual machines. If you get 8.8.8.8 dns trough dhcp, it was most like manually configured somewhere.

1) You can override this using horizon or cli for every subnet:

neutron subnet-(update|create) --dns-nameservers list=true 192.168.0.254 192.168.1.254 ...

2) Or you can specify global dnsmasq options in the file defined with "dnsmasq_config_file" parameter of the dhcp agent config.

dhcp-option=6, x.x.x.x, y.y.y.y

Upstream DNS forwarders are defined in the dhcp agent config with dnsmasq_dns_servers=8.8.8.8,4.4.4.4 parameter

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and if dnsmasq is running in a namespace, then the subnet will need to be attached to a router that is connected to an external network.

darragh-oreilly gravatar imagedarragh-oreilly ( 2014-12-16 13:31:53 -0500 )edit

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Asked: 2013-09-13 22:13:48 -0500

Seen: 1,271 times

Last updated: Dec 16 '14