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Well if that's the case then the metadata wouldn't work for every instance
that ARP'ed for the address and got the wrong response first.

On Thu, Dec 3, 2015 at 3:56 PM, Gilles Mocellin <
gilles.mocellin at nuagelibre.org> wrote:

> Hum, I don't think so. Things like hostname must be only known by the
> neutron instance of one region...
>
> Le 03/12/2015 00:01, Kevin Benton a écrit :
>
>> Are both metadata servers able to provide metadata for all instances of
>> both sides? If so, why not disable isolated metadata on one of the sides so
>> only one of the DHCP agents will respond?
>>
>>
>> On Thu, Nov 26, 2015 at 6:49 AM, <gilles.mocellin at nuagelibre.org <mailto:
>> gilles.mocellin at nuagelibre.org>> wrote:
>>
>>     Hello stackers !
>>
>>     Sorry, I also cross-posted that question here
>>
>> https://ask.openstack.org/en/question/85195/two-regions-and-so-two-metadata-servers-sharing-the-same-vlan/
>>
>>     But I think I can reach a wider audience here.
>>
>>     So here's my problem.
>>
>>     I'm facing an non-conventional situation. We're building a two
>>     region Cloud to separate a VMware backend and a KVM one. But both
>>     regions share the same 2 VLANs where we connect all our instances.
>>
>>     We don't use routers, private network, floating IPs... I've
>>     enabled enable_isolated_metadata, so the metadata IP is inside the
>>     dhcp namespace and there's a static route in the created instances
>>     to it via the dhcp's IP. The two DHCPs could have been a problem
>>     but we will use separate IP ranges, and as Neutron sets static
>>     leases with the instances MAC address, they should not interfere.
>>
>>     The question I've been asked is whether we will have network
>>     problems with the metadata server IP 169.254.169.254, that will
>>     exist in 2 namepaces on 2 neutron nodes but on the same VLAN. So
>>     they will send ARP packets with different MAC, and will perhaps
>>     perturb access to the metadata URL form the instances.
>>
>>     Tcpdump shows nothing wrong, but I can't really test now because
>>     we haven't got yet the two regions. What do you think ?
>>
>>     Of course, the question is not about why we choose to have two
>>     regions. I would have chosen Host Agregates to separate VMware and
>>     KVM, but cinder glance should have been configure the same way.
>>     And with VMware, it's not so feasible.
>>
>>     Also, if we can, we will try to have separate networks for each
>>     regions, but it involves a lot of bureaucracy here...
>>
>>     _______________________________________________
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>>
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>>
>>
>>
>>
>> --
>> Kevin Benton
>>
>
>
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-- 
Kevin Benton
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