[ILUG] Slow IPv6 when using bridge networking on CentOS 6.x

[Jean Francois Bucas]

What if you try to give an IPv6 to your bridge interface and try your
speed test from that address?

Idea is to find if the problem is between the bridge and outside or
between the VM and the bridge;  between the VM and bridge, there's a
good change that your Hypervisor is somehow filtering the traffic (eg: #
virsh nwfilter-list )

Also on CentoOS 5.x, the problem was only on some *intelligent* network
cards, if you have access to the HW, you can try a different one.

Another idea would be to try a different OS, to see if a different
kernel version/options would make a difference.

Jef


On 16/12/12 18:56, FRLinux wrote:
> I ran into this one a while back where CentOS 5.x used to be slow on VM
> running through the network bridge. The fix at the time was to issue an :
> ethtool -K eth0 tso off. So i did just that and here are my current
> settings.
> 
> # ethtool -k eth0
> Offload parameters for eth0:
> rx-checksumming: on
> tx-checksumming: off
> scatter-gather: off
> tcp-segmentation-offload: off
> udp-fragmentation-offload: off
> generic-segmentation-offload: off
> generic-receive-offload: on
> large-receive-offload: off
> 
> Now this unfortunately does not work anymore. I have searched a few forums
> and no one seems to have run into that one.
> 
> Here are the speeds compared on v4 and v6 (this is from HEAnet's mirror)
> 
> wget -O /dev/null -c
> http://ftp.heanet.ie/pub/centos/5.8/isos/x86_64/CentOS-5.8-x86_64-bin-2of8.iso
> Resolving ftp.heanet.ie... 2001:770:18:aa40::c101:c140, 193.1.193.64
> Connecting to ftp.heanet.ie|2001:770:18:aa40::c101:c140|:80... connected.
> 15,804,132  1.23M/s  eta 44m 35s
> 
> wget -4 -O /dev/null -c
> http://ftp.heanet.ie/pub/centos/5.8/isos/x86_64/CentOS-5.8-x86_64-bin-2of8.iso
> 47,537,840  7.70M/s  eta 14m 51s
> 
> Tested this several times over, this is giving me the same results. If I
> disable the bridging mode on the network card, i get full speed over IPv6.
> 
> Anyone?
> 
> Cheers,
> Steph
> 

-- 
Jean-Francois Bucas
IT System Administrator
School of Theoretical Physics
Dublin Institute for Advanced Studies
10 Burlington Road
Dublin 4
Tel. +353 1 614 0132