[ovs-discuss] Over-mtu packets in GRE tunnel

Jesse Gross jesse at nicira.com
Wed Oct 3 18:59:02 UTC 2012


On Wed, Oct 3, 2012 at 11:43 AM, Jeff Welsch <jeff at jeffwelsch.com> wrote:
> Hello,
>
> When forwarding traffic through a GRE tunnel I am receiving error messages about over-mtu packets: openvswitch: br0: dropped over-mtu packet: 1810 > 1500.  The packet size varies and on my Linux console I am receiving notification that net_ratelimit is suppressing callbacks of a large amount of similar messages.  I am using 1.8.90 as a linux module with kernel 3.4.3.
>
> ifconfig br0 mtu 9000 does not have an effect.  The mtu on my eth interfaces is set to 9000.  eth0 doesn't belong to br0.
>
> Is this possibly a bug in that codebase?  Is there a version of the 1.8 tree that may be more stable if so?  I would use 1.7.1 but am interested in the no-packet-in feature of 1.8.x.

I'm guessing that you're using Linux GRE devices, in which case you
have to raise the MTU on that device.



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