[Openstack] Flat provider_network with vlan tagged interface or vlan provider_network with untagged interface

Abhijeet Rastogi abhijeet.1989 at gmail.com
Wed Dec 3 04:10:36 UTC 2014

Hey Kevin,

Thanks for clearing that out. So, I essentially achieve the same
thing. To summarize, if provider networks need vlan, it mostly makes
sense to just use vlan and ditch trying to setup "flat" provider

On Wed, Dec 3, 2014 at 9:33 AM, Kevin Benton <blak111 at gmail.com> wrote:
> Setting up the interfaces manually and using a flat network doesn't scale
> well when you want to do it hundreds of times. Using ML2+linuxbridge will do
> the same thing in an automated fashion.
> On Tue, Dec 2, 2014 at 6:32 PM, Abhijeet Rastogi <abhijeet.1989 at gmail.com>
> wrote:
>> Hi everyone,
>> This is a very basic doubt and I'm trying to understand this
>> fundamental thing about creating networks in neutron. My ultimate goal
>> is to have all instances contain just one interface and a public IP on
>> them. Now, this public IP can only exist in a specific VLAN, lets say,
>> they'll only exist on eth0.123 (the is a vlan tagged interface on the
>> host and I can directly bind public IPs to them and they work
>> perfectly). I'm using linux bridge + ML2 as the plugin for neutron.
>> So, the ultimate goal will be something like:
>> [root at compute1 ~]# brctl show
>> bridge name     bridge id               STP enabled     interfaces
>> brq732eb7f9-16          8000.002590c6438e       no              eth0.123
>>                       tap81474f06-29
>> Now, with my limited knowledge, there are 2 ways of doing this:-
>> 1. Create the vlan tagged interface manually and then setup "flat"
>> provider networking with physical_interface_mappings set with
>> eth0.123.
>> 2. Use a "vlan" provider network and mention "123" as the vlan id in that.
>> I observed that, both of these approaches eventually create the same
>> kind of bridge configuration. Can anyone explain what's going on and
>> when to use what? I'm sure I'm missing a key concept and I'll be glad
>> if someone can clear that for me.
>> --
>> Cheers,
>> Abhijeet Rastogi (shadyabhi)
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> --
> Kevin Benton

Abhijeet Rastogi (shadyabhi)

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