[openstack-dev] [devstack] [neutron] Progress, and current problems

Mike Spreitzer mspreitz at us.ibm.com
Tue Jan 5 08:02:15 UTC 2016

I have been trying to get 
working on Ubuntu 14.04 (updated to the latest, which includes kernel 
3.19).  With the latest sources and a sufficiently recent OVS, the 
one-node install pretty much works!  I added to local.conf only: (a) 
IP_VERSION=4, to avoid issues with v6, and (b) some settings to get logs 
saved to files without coloring.

In particular, what I have done regarding OVS is to download 2.4 and build 
the .deb packages according to the instructions.  I used the kernel 
datapath from the linux kernel 3.19.  I installed the openvswitch-common 
and openvswitch-switch .debs that I built.

I think the doc should be enhanced to discuss IPv6.  I tried once without 
the `IP_VERSION=4`, and the resulting IPv6 config was not good.

IMHO the default should be to keeps logs in files without coloring, 
because that is the most user-friendly.  I think that for DevStack the 
defaults should be friendly to newbies, since this is where they start.

I then went on to 
, and ran into MTU problems.  All MTUs come out to be 1500, which just 
does not work (due to the tunneling overhead).

I then tried a fresh DevStack install with a revised local.conf derived 
.  Specifically, this is what I added to my local.conf for MTU issues:


physical_network_mtus = public:1450

That got me MTUs of 1450 on the router and DHCP ports but not the VM 
plumbing.  Perhaps I read too much into the word "keep".

Then I added

network_device_mtu = 65000

to the DEFAULT section of nova.conf, then restarted all the nova 
processes.  I created a new VM after that.  The result was that the 
qbr..., qvo..., qvb..., and tap... network interfaces in the main netns 
have MTU of 65000 --- and eth0 inside the VM has an MTU of 1500.

So then I changed the network_device_mtu setting in nova.conf to 1450, 
restarted all the nova processes again, and made another new VM.  Now the 
qbr..., qvo..., qvb..., and tap... network interfaces in the main netns 
have MTU of 1450 but the VM still got an MTU of 1500 on its eth0.

In my logs directory, `grep 'Running command' *.log | grep set | grep -i 
mtu` finds only the setting of the MTUs of the router and DHCP stuff --- 
nothing for any of the VMs.


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