Comment 4 for bug 1733987

On 30 November 2017 at 06:47, Armando M. <email address hidden> wrote:

>
> On Thu, Nov 30, 2017 at 03:20 venkata anil <email address hidden>
> wrote:
>
>> To reach the DHCP server, why the request from vm is going through
>> router?
>>
>
> It’s not the dhcp server that is required to reach but the dns authority
> behind it. This may need the router.
>

Think about a situation where the DNS for the DHCP agent is eg. 8.8.8.8,
and the guest VM's DNS is 192.168.1.2 (the DHCP interface). The DNS VM's
request hits the DHCP namespace but it can't get out as it can't reach the
router to go and resolve the name of whatever node the VM's need to reach.

HTH
Armando

>
>> --
>> You received this bug notification because you are subscribed to the bug
>> report.
>> https://bugs.launchpad.net/bugs/1733987
>>
>> Title:
>> name resolution error with DVR+HA routers
>>
>> Status in neutron:
>> In Progress
>>
>> Bug description:
>> Steps to repro:
>>
>> * Deploy with multiple DHCP agents per network (e.g. 3) and multiple L3
>> agents per router (e.g. 2)
>> * Create a network
>> * Create a subnet
>> * Create a DVR+HA router
>> * Uplink router to external network
>> * Deploy a VM on the network
>>
>> The resolv.conf of the VM looks something like this:
>>
>> cat /etc/resolv.conf
>> search openstack.local
>> nameserver 192.168.0.2
>> nameserver 192.168.0.4
>> nameserver 192.168.0.3
>>
>> Where .2, .3. and .4 are your DHCP servers that relay DNS requests.
>>
>> Name resolution may fail when using one of these servers, due to the
>> lack of qrouter namespace on one of the network nodes associated with
>> the qdhcp namespace hosting the DHCP service for the network.
>>
>> Expected behavior:
>>
>> All nameservers can resolve correctly.
>>
>> This happens in master and prior versions.
>>
>> To manage notifications about this bug go to:
>> https://bugs.launchpad.net/neutron/+bug/1733987/+subscriptions
>>
>