[ovs-discuss] Open vSwitch balance-slb bond mode with two upstream switches

Ben Pfaff blp at ovn.org
Mon Jul 22 18:18:48 UTC 2019

On Fri, Jul 19, 2019 at 02:22:18PM -0700, Dan Sneddon wrote:
> On Fri, Jul 19, 2019 at 7:46 AM Grzegorz <juszczak.grzegorz at gmail.com>
> wrote:
> > Hi Jason
> >
> > I have the same doubts - I would like to connect balance-slb in OpenStack
> > Rocky to two separate switches.
> >
> > I see you wrote this post a few years ago.
> > Have you figured it out finally?
> >
> > Thank you in advance for your reply
> >
> > BR
> > Grzegorz Juszczak
> >
> This only works if the two switches are clustered, i.e. two or more chassis
> running as a single logical switch.
> The issue is that balance-slb will only use one link for a MAC+VLAN, but
> when rebalancing happens the traffic may start using the other port. If the
> switch attached to the original port doesn't know that the traffic is now
> using the other port/different switch, then traffic to the OVS bond may be
> lost.
> You can use active-backup with OVS bonds and two switches, or attach a
> bond/team using a different bonding technique (Linux kernel bonds, teamd
> adapter teams, etc.) that supports disparate switches and then attach that
> bond to OVS. There aren't many good options for attaching to multiple
> switches, so I try to use switches that can be clustered when I'm not using
> a chassis switch.
> Look into teamd, it has more options for controlling how your traffic is
> load balanced, and you can choose your own hash combinations. I've
> configured OpenStack deployments with teams attached to OVS bridges for
> Neutron. The best documentation I've found so far is here, but you may need
> to adjust depending on Linux distribution:
> https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/networking_guide/ch-configure_network_teaming

This is a helpful email.  Is there a chance you'd be willing to rephrase
it as a FAQ question and answer?  Then it'd be useful to lots of people.

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