[Openstack] Very slow connectivity from within tenant network - GRE

Rick Jones rick.jones2 at hp.com
Tue Oct 22 15:25:28 UTC 2013

On 10/22/2013 01:32 AM, Martinx - ジェームズ wrote:
> Stackers,
> I'm trying to put my Havana into production and I'm facing a very
> strange problem.
> The Internet connectivity from tenant's subnet is very, very slow. It is
> useless in fact... I can not even use "apt-get update" from a Instance.
> The following command works (apt update from the tenant namespace):
> ---
> root at net-node-1:~# ip netns exec qrouter-XXXXXXXXX aptitude update
> ---
> But not from the tenant subnet...
> I'm following this topology:
> http://docs.openstack.org/trunk/install-guide/install/apt/content/section_use-cases-tenant-router.html
> Already tried to change MTUs (via DHCP agent)... Nothing had fixed this
> weird issue.
> Any thoughts?!
> Right now, my "aptitude safe-upgrade" will take 2 days to download
> 60MB... During this network outages, even the SSH session stops
> responding for a few seconds...
> Everything else seems to be working as expected, as for example, DHCP,
> Floating IPs, Security Groups...
> Sometimes, even the first ssh connection to the Instance Floating IP,
> have a lag.

It is but a guess, but I wonder if, even with changing MTUs (to what 
values?) you may still be experiencing a PathMTU+ICMP blackhole problem 
accessing nodes on the Internet.  Can you access something that is a bit 
"closer" but still outside your stack so you have a shot at looking at 
netstat statistics on the sender and/or get packet traces on the sender?

You could still try taking packet traces at the instance or perhaps the 
namespace and try to discern packet losses at the receiving side, though 
it can be a bit more difficult.

rick jones

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