[ovs-discuss] The network speed is low when use vlan on ovs
Kris zhang
zhang.kris at gmail.com
Fri Mar 29 05:54:50 UTC 2013
Thanks a lot
On Fri, Mar 29, 2013 at 1:07 PM, Ben Pfaff <blp at nicira.com> wrote:
> On Fri, Mar 29, 2013 at 01:05:16PM +0800, Kris zhang wrote:
> > So my question is why the network speed is slow when use vlan in OVS?
>
> There's a huge section in the FAQ about VLANs. Please read it.
>
> Some relevant parts:
>
> Q: VLANs don't work.
>
> A: Many drivers in Linux kernels before version 3.3 had VLAN-related
> bugs. If you are having problems with VLANs that you suspect to be
> driver related, then you have several options:
>
> - Upgrade to Linux 3.3 or later.
>
> - Build and install a fixed version of the particular driver
> that is causing trouble, if one is available.
>
> - Use a NIC whose driver does not have VLAN problems.
>
> - Use "VLAN splinters", a feature in Open vSwitch 1.4 and later
> that works around bugs in kernel drivers. To enable VLAN
> splinters on interface eth0, use the command:
>
> ovs-vsctl set interface eth0
> other-config:enable-vlan-splinters=true
>
> For VLAN splinters to be effective, Open vSwitch must know
> which VLANs are in use. See the "VLAN splinters" section in
> the Interface table in ovs-vswitchd.conf.db(5) for details on
> how Open vSwitch infers in-use VLANs.
>
> VLAN splinters increase memory use and reduce performance, so
> use them only if needed.
>
> - Apply the "vlan workaround" patch from the XenServer kernel
> patch queue, build Open vSwitch against this patched kernel,
> and then use ovs-vlan-bug-workaround(8) to enable the VLAN
> workaround for each interface whose driver is buggy.
>
> (This is a nontrivial exercise, so this option is included
> only for completeness.)
>
> It is not always easy to tell whether a Linux kernel driver has
> buggy VLAN support. The ovs-vlan-test(8) and ovs-test(8) utilities
> can help you test. See their manpages for details. Of the two
> utilities, ovs-test(8) is newer and more thorough, but
> ovs-vlan-test(8) may be easier to use.
>
> Q: VLANs still don't work. I've tested the driver so I know that it's OK.
>
> A: Do you have VLANs enabled on the physical switch that OVS is
> attached to? Make sure that the port is configured to trunk the
> VLAN or VLANs that you are using with OVS.
>
> Q: Outgoing VLAN-tagged traffic goes through OVS to my physical switch
> and to its destination host, but OVS seems to drop incoming return
> traffic.
>
> A: It's possible that you have the VLAN configured on your physical
> switch as the "native" VLAN. In this mode, the switch treats
> incoming packets either tagged with the native VLAN or untagged as
> part of the native VLAN. It may also send outgoing packets in the
> native VLAN without a VLAN tag.
>
> If this is the case, you have two choices:
>
> - Change the physical switch port configuration to tag packets
> it forwards to OVS with the native VLAN instead of forwarding
> them untagged.
>
> - Change the OVS configuration for the physical port to a
> native VLAN mode. For example, the following sets up a
> bridge with port eth0 in "native-tagged" mode in VLAN 9:
>
> ovs-vsctl add-br br0
> ovs-vsctl add-port br0 eth0 tag=9 vlan_mode=native-tagged
>
> In this situation, "native-untagged" mode will probably work
> equally well. Refer to the documentation for the Port table
> in ovs-vswitchd.conf.db(5) for more information.
>
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