[lxc-users] Networking issues with LXC containers in EC2

Peter Steele pwsteele at gmail.com
Wed Apr 27 12:49:46 UTC 2016

On 01/12/2016 07:03 PM, Fajar A. Nugraha wrote:
> On Tue, Jan 12, 2016 at 9:29 PM, Peter Steele <pwsteele at gmail.com> wrote:
>> On 01/12/2016 05:59 AM, Fajar A. Nugraha wrote:
>>> On Tue, Jan 12, 2016 at 8:40 PM, Peter Steele <pwsteele at gmail.com> wrote:
>>>> I should have added that I have no issue running our software on a single
>>>> EC2 instance with containers running on that instance. We can assign
>>>> multiple IPs to the instance itself, as well as to the containers running
>>>> under the instance, and the containers can all communicate with each
>>>> other
>>>> as well as with the host.
>>> can the containers in that setup communicate with systems outside the
>>> host (e.g. access the internet)?
>>> if "no", then you might hit the multiple mac problem
>> Sadly the answer is no. They cannot even ping another host in the same
>> VPC...
> Looks like multiple mac problem. As in, EC2 only allows one mac from
> your interface.
> Proxyarp should work:
> (1) Make SURE your EC2 instances (I'd call them "host" from now on)
> supports multiple IPs (private or elastic/public IPs, depending on
> your needs). The easiest way is to add those IPs to your host
> interface, make sure that that new IP can be accessed (e.g. ping that
> IP from another host), and then remove it.
> (2) Enable proxy arp on the host
> echo 1 > /proc/sys/net/ipv4/conf/eth0/proxy_arp
It turned out that proxy arp was indeed the solution here, but a few 
other parameters had to be set as well. I just need to run the following 
commands on each EC2 instance:

echo 1 > /proc/sys/net/ipv4/conf/br0/forwarding
echo 1 > /proc/sys/net/ipv4/conf/br0/proxy_arp_pvlan
echo 1 > /proc/sys/net/ipv4/conf/br0/proxy_arp
echo 0 > /proc/sys/net/ipv4/conf/all/send_redirects
echo 0 > /proc/sys/net/ipv4/conf/br0/send_redirects

With these settings, my containers and hosts can all talk to each other 
just like they were all residing on the same subnet. An easy solution in 
the end.


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