[neutron] Can br-ex and br-tun use the same interface?

Zhengyu Pan zhengyupann at 163.com
Tue Feb 18 12:03:52 UTC 2020

Thank you. Do i  only need to add a patch port  that connects br-ex with br-tun? And create a port that binds tunnel ip  in br-ex?



At 2020-02-18 18:39:25, "Sean Mooney" <smooney at redhat.com> wrote:
>On Tue, 2020-02-18 at 19:12 +0800, Zhengyu Pan wrote:
>> hi,
>>     I have only two physical  interfaces. In my deploying, network node and compute node are the same. 
>> Can Bridge br-tun and br-ex use the same interface when using vxlan network type ? management network use the other
>> interface?
>yes they can. the way this works wehn ovs encapsulates teh packet the vxlan tunnel endpoint ip is used to lookup what
>interface to transmit the packet on. so to use the same interface for both tunnels and provider networks you need
>to assign the tunnel endpoint ip to br-ex. ovs has a special operation at the dataplane level call out_port which is
>different form output. if ovs detects that the the source ip adress of the vxlan tunnel is assocaited with a bridge,
>in this case  br-ex and if that bridge is connect to the bridge with the tunnel port directly or indirectly via patch
>ports i it will use the out_port action to skip sending the packet via the kernel networking stack.
>so if you use use an interface that is attached to an ovs bridge it will actully imporve performance in general.
>that said adding the tunnel endpoint ip to the br-tun and adding an interface to br-tun used to crash ovs. i dont know
>if that was ever fixed but i would recommend not trying and just adding the tunnel enpoint ip to br-ex.
>not that this is the recommended way to deploy ovs-dpdk as if you dont add the tunnel endpoint ip to br-ex all packets
>that use vxlan will be sent via the kernel which will significantly reduce performance.
>im not sure if this works with hardwar offloaded ovs but i would consider it a bug if it did not.
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