[Openstack-operators] Virtual Instance can't obtain IP address (OpenStack Havana)

Alvise Dorigo alvise.dorigo at pd.infn.it
Wed Jan 29 18:01:43 UTC 2014

Hi David, 

> On your network node, check the NIC settings for various offloading
> "optimizations":
>    $ ethtool -k eth0 | grep offload
>    tcp-segmentation-offload: off
>    udp-fragmentation-offload: off [fixed]
>    generic-segmentation-offload: off
>    generic-receive-offload: off
>    large-receive-offload: off [fixed]
>    rx-vlan-offload: on
>    tx-vlan-offload: on

I issued that command on my eth2 NIC which is connected to the data-network

[root at network ~]# ethtool -k eth2 | grep offload
tcp-segmentation-offload: on
udp-fragmentation-offload: off
generic-segmentation-offload: on
generic-receive-offload: off
large-receive-offload: off

On network node I’ve 3 networks:


On compute I’ve 2 networks:

Did I do correctly ?

The offload is on. Should I change it ? how ?

> We recently solved this problem at $WORK by disabling GRO on our network
> node.
> The other issue we've come across that may be related is MTUs: since Open
> vSwitch 1.9+ got rid of Path MTU Discovery, you may need to adjust your
> MTUs:
>  http://techbackground.blogspot.ca/2013/06/path-mtu-discovery-and-gre.html

In that article they talk about a GRE setup, but I choosed local (CONFIG_NEUTRON_OVS_TENANT_NETWORK_TYPE=local). Can I use that guide anyway ?

> There are two ways to fix this: if your network infrastructure has jumbo
> frames (1500+) enabled, change the hardware NICs to have an MTU of 1546
> (or larger). If you do not have jumbo frames enabled, configure the guests
> to have an MTU of 1454 or smaller.
> One or both of these things (GRO and MTU) will probably be needed for a
> properly functioning virtual network.

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