slow download from instances in Kilo release, 3 nodes version.

asked 2015-08-06 08:18:50 -0500

brahimo gravatar image

updated 2015-08-06 08:44:35 -0500

Hi everyone.
i need some help about slowness of wget from my instances. I have installed 3 nodes' KILO release of openstack on fedora 21 as described in the official documentation. everything is ok during the installation and verifications proposed at the docs.
right now i runned some instances based on fedora 22 cloud image .. but yum doesnot work correctly at the begining i thought it was a problem with repository but checked nothing appeared wrong then i choosed to download my rpm using wget but i noticed that it is too slow and if the file is just more than 10MB it interrupts before termnating download.
during the download by an instance form an external server I checked traffic im my external interface enp0s3 by tcpdump i see a lot of packets coming from external server of length 1420, in parallel with a tcpdump of router interface qg-xxxxxx i see one packet of length 1420 then a lot of packet with length 140 that come slowly then another packet of 1420 and so on.

on external interface enp0s3
-------------------------------------
external_serer.10361 > 10.0.2.103.50746 (my instance) :length 1420

on vRouter qg interface
--------------------------------
external_server.50280 > network.49281 : length 1420
network.ssh > 10.0.2.15.34502 : length 140


any help what could be the problem.

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Comments

Check the MTU on the VMs, If you are running the MTU on the nics on the physical hosts at 1500, your VMs will need to be under 1450 to work properly. Small packets will make it through fine, but anything with a payload will fragment.

jdexter gravatar imagejdexter ( 2015-08-10 13:02:03 -0500 )edit

You can either set the MTU on the VMs or bring all of the MTUs on all the physical nics and switches (on the tunnel interfaces) up to 1550.

jdexter gravatar imagejdexter ( 2015-08-10 13:02:39 -0500 )edit