If the original packets are of length <= 1400, then they are successfully transmitted through the tunnel. Only when a packet is greater than ~1480 it gets dropped. You are right the ip stack is fragmenting the large packets, but because some of them are a notch below 1500 they are passed as is. For these packets, adding gre/ip headers would increase their size to > 1500bytes. Subsequently they are dropped. The reason may be because the packets are already beyond the ip stack of the host, and no further manipulation of the packets is done after this point.
I may be confused as to the right sequence of processing here. Reducing the size of packets, via MTU tweaking, seems to be a common practice when gre is used. Any ideas on this ? Thanks Ted On Wed, Aug 21, 2013 at 12:40 PM, Jesse Gross <[email protected]> wrote: > On Tue, Aug 20, 2013 at 6:04 PM, Theodore Elhourani > <[email protected]> wrote: > > We are sending traffic over gre on ovs. Some of the packets are large and > > will not go through to the other end of the gre tunnel because hardware > > switches in between are not forwarding packets > 1500B. > > > > Is there a way to have ovs itself segment the packets into MTU-sized > packets > > before putting them on the gre port ? > > Is the MTU of your local Ethernet interface 1500 bytes? If so, the IP > stack should fragment the GRE packets if necessary. >
_______________________________________________ discuss mailing list [email protected] http://openvswitch.org/mailman/listinfo/discuss
