[ovs-discuss] OpenVSwitch looped topology without bonds/STP

Raymond Burkholder ray at oneunified.net
Wed Mar 27 22:51:37 UTC 2019


On 2019-03-27 3:19 p.m., Colton Powell wrote:
> Anyways, I was thinking the same thing as you: It seems I will have to disable STP + the default forwarding rules, and then write flows to get ARP, etc. working as intended. I just wanted to see if there was some other, simpler solution that perhaps I was missing here.

In the long run, the simpler way is to consider building layer 3 
networks, and using OVS for overlay layer 2 tasks.

> As far as your questions go: Our control channel is in-band, and we are running all OVS-only switches. It’s a pretty straightforward setup, but evidently now I’m not sure it quite fulfills our needs.

hmmm, quite possibly, depending upon what your ultimate goals are.

> Also, can you explain how in-band control cause more issues for us, rather than less?

In a nutshell, one of possibly several examples ... if you were to 
continue with the layer 2 concept, and thus being forced into disabling 
most flows and re-enabling them under coordinated control, you'll end up 
with issues of bootstrapping the links (possibly multiple hops) between 
the controller and OVS.

In addition, if you were to stick with spanning tree enabled, you'll 
have other issues for flow rules, as well as the controller:  if links 
break or go down, then spanning tree can take quite some time (measured 
in seconds) to re-converge, and in the meantime, other links may or may 
not go in and out of forwarding, causing all sorts of issues for 
forwarding as well as inbound control plane traffic.

> 
> Thanks again!
> 
> Colton
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