[Lxc-users] Networking issues with LXC

Daniel Lezcano daniel.lezcano at free.fr
Wed Feb 10 21:20:07 UTC 2010

Michael B. Trausch wrote:
> Hello,
> I am running LXC version 0.6.5, with kernel  I am having some 
> pretty significant troubles getting networking to reliably work with the 
> containers.  That is to say, the host name is doing just fine, and 
> answers network requests all the time.  However, the containers 
> sometimes fail to respond to network for requests for several seconds 
> and several connection attempts.  This isn't a problem in that it's 
> rejecting connections on the ports specifically; it's as if there is no 
> machine on my network with the IP address assigned to the container, 
> until it comes alive again and answers the network.
> If I work with a container after getting a connection, I can reach that 
> container for several minutes (usually---sometimes it will cut off a 
> connection, though, and then it is again as if that IP address doesn't 
> exist on my network).
> I'm out of options as far as getting this working:  This network 
> configuration works with containers under OpenVZ or full virtual 
> machines in KVM, where the virtualized network cards are attached to the 
> bridge.  The IP configuration is handed out by DHCP, (except for my 
> public IP addresses, which are manually assigned) and the IP addresses, 
> netmasks, default routes, gateways, broadcast addresses, and so forth 
> are all correct.  Nonetheless, the networking is *extremely* unreliable.
> I don't know how to provide additional information to attempt to work 
> through a problem like this; any guidance in this area would be greatly 
> appreciated.
Mmh, hard to answer.

Can you give the following information:

 * how many containers are running on the host ?

For the host and the containers:
 * 'ip addr show'
 * ip neigh show
 * 'brctl show'

And a tcpdump :

 tcpdump -i any dst or src <containerip>

And then try to ping or  connect to/from the container to make tcpdump 
show something.

  -- Daniel

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