[Openstack] Floating IP issues with multiple physical NICs, subnets

Scott Severtson ssevertson at digitalmeasures.com
Tue Aug 26 15:23:00 UTC 2014


On Fri, Aug 22, 2014 at 11:06 AM, Scott Severtson <
ssevertson at digitalmeasures.com> wrote:

> All,
> We're trying to configure the following scenario - Compute nodes with
> multiple physical NICs, each dedicated to a specific function/subnet:
> Management/Private:
> Storage:
> External/Floating/DMZ:
> We currently have two Nova Flat DHCP Networks (not using Neutron due to
> lack of multi-host support) configured for both Storage and Management, and
> are able to get appropriate connectivity in our VMs on each of these
> subnets.
> However, when we try to assign a floating IP to a VM in the External
> subnet, we see problematic routing of packets. Packets reach the VM, the VM
> responds, and then the response packets are often routed back out the
> Management subnet. The behavior is inconsistent: some VMs can reliably
> route packets back out the External NIC/subnet, and everything works; other
> VMs consistently respond via the Management subnet; still others seem to
> flip-flop between responding over the External and Management subnets.
> When packets are sent over the incorrect NIC, our switches drop them, as
> we do not allow routing between subnets.
> How we ensure that outbound/response packets from a VM are routed over the
> NIC that originally received the request packets in the first place?
> Connection Tracking *is* specified in our IP Tables rules on the Compute
> nodes, as automatically configured by Nova Network.
> Any thoughts? Are we trying to configure a scenario not supported by
> OpenStack?
> Thanks,
> --Scott
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