I think the only way to fix this issue is by configuring other devices in your network with an MTU < 1500. This way, when your OVS gets the packet, it can slap on additional headers and still get the packet across since the overall length would be <= 1500.
On Sat, Jul 25, 2015 at 11:00 AM, Dave Waters <davewaters1...@gmail.com> wrote: > In my case all my NIC cards can support jumbo frames. So i can really send > a 1600 byte packet. However, i am being restricted by the OVS's internal > port's MTU which is fixed to 1500. As a result i am unable to send out > larger packets (because of the VXLAN header addition). Can somebody please > help me here? > > Dave > > On Fri, Jul 24, 2015 at 10:39 PM, Dave Waters <davewaters1...@gmail.com> > wrote: > >> That wouldnt work since anybody connected to portA and sending a 1500 >> byte packet, would be unable to do so. >> >> Is there a known limitation wherein i can increase the MTU of an internal >> bridge port? >> >> Dave >> >> On Fri, Jul 24, 2015 at 10:32 PM, Joe Stringer <joestrin...@nicira.com> >> wrote: >> >>> Have you tried decreasing the MTU of portA such that packets are >>> encapsulated they're <=1500B? >>> >>> On 23 July 2015 at 08:19, Dave Waters <davewaters1...@gmail.com> wrote: >>> > Its not. But how do i ensure that my packet does not get dropped >>> somewhere >>> > downstream, since i have now increased it beyond the original value? >>> > >>> > On Thu, Jul 23, 2015 at 7:49 PM, gowrishankar >>> > <gowrishanka...@linux.vnet.ibm.com> wrote: >>> >> >>> >> On Thursday 23 July 2015 04:16 AM, Dave Waters wrote: >>> >>> >>> >>> Hi, >>> >>> >>> >>> I have two ports in my OVS bridge. I receive packets from one port >>> >>> (portA) and i send them out of the other (portB). When i send out the >>> >>> packets, they are VXLAN tunneled to the other end. >>> >>> >>> >>> Now, the default MTU of all ports (including the bridge port) is >>> 1500 in >>> >>> my setup. >>> >>> >>> >>> The issue is that when i get a 1500 byte packet on portA, i try to >>> push >>> >>> it out on portB after slapping on the VXLAN headers. This results in >>> a >>> >>> packet size thats greater than what portB can handle, and hence the >>> packets >>> >>> are dropped. >>> >>> >>> >> >>> >> Is increasing MTU of portB to 1550 (to accommodate additional 50 bytes >>> >> when no vlan taged) a constraint in your setup ? >>> >> >>> >> >>> >>> I know that OVS does not handle IP fragmentation/reassembly, so how >>> do we >>> >>> deal with this situation? I dont think we can rely on path MTU >>> discovery >>> >>> since not all applications do PMTU before spewing out packets. Any >>> ideas, >>> >>> anybody? >>> >>> >>> >>> Warm regards, >>> >>> Dave >>> >>> >>> >> >>> >> -- >>> >> Regards, >>> >> Gowrishankar M >>> >> >>> > >>> > >>> > _______________________________________________ >>> > discuss mailing list >>> > discuss@openvswitch.org >>> > http://openvswitch.org/mailman/listinfo/discuss >>> > >>> >> >> > > _______________________________________________ > discuss mailing list > discuss@openvswitch.org > http://openvswitch.org/mailman/listinfo/discuss > >
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