[lxc-users] Need help with static IP address -- Simplest use case.

[Michael Johnson]

Thank you Fajar. I misunderstand many concepts. Your response here is
the best documentation I've found on exactly what is happening behind
the scenes when using 'lxc network create'. I still don't understand why
entries are needed & created in iptables as a result of running that
command, but that's a discussion for another day.

You also recommend I not "rely on lxc config file [for a static IP], but
rather set it up directly in the container OS." I did it both places.
I'm not sure which is overriding which.

-Mike

Fajar A. Nugraha wrote:
> On Sat, Jun 10, 2017 at 12:38 PM, Michael Johnson
> <johnson at cognitech-ut.com <mailto:johnson at cognitech-ut.com>> wrote:
> 
>     Thanks for all the suggestions. I seem to have magically fixed it. When
>     I changed the parent from lxdbr0 to br0 it now works. Lxdbr0 was a
>     'network' I created with 'lxc network create' and br0 was the host
>     bridge I configured by hand. This probably makes sense to someone who
>     understands how lxd works. There seems to be a conflict between static
>     ip addresses and the way 'lxc network create' defines a bridge. Possibly
>     I missed a config option for routing that is necessary when static ip is
>     combined with 'lxc network create'.
> 
> 
> 
> You seem misunderstood some concept:
> 
> (1) lxc network create 
> - basically creates a bridge, managed by lxd, optionally with its own
> DHCP server (dnsmasq). 
> - it is a SEPARATE network from your host's network (e.g. eth0)
> - you CAN assign "static ip" on this bridge. Or to be more accurate,
> configure the dhcp server to always assign a specific IP for that container
> 
> (2) host bridge (should be br0 in your example)
> - on the same L2 network with your host interface
> - use whatever DHCP server available on the network (if available). You
> should NOT create your own dhcp server on this bridge
> 
> (3) container's interface config
> - there are some ways to setup an container's IP address
> - a container can, most of the times, overide IP address assignment on
> lxc config
> - the best setup, IMHO, is to either:
> --> have container using dhcp, and setup the DHCP server (which include
> lxd's dnsmasq) to assign persistent ip address. This is the example
> listed on
> https://stgraber.org/2016/10/27/network-management-with-lxd-2-3/ .  OR
> --> configure the container OS (e.g. on /etc/network/interfaces, or
> equivalent distro location) to use static IP
>  
> 
>     Did not work:
> 
>     devices:
>       default:
>         ipv4.address: 192.168.0.36/24 <http://192.168.0.36/24>
>         name: eth0
>         nictype: bridged
>         parent: lxdbr0
>         type: nic
> 
> 
> Which is the correct behavior. Since lxdbr0 is on separate network from
> your host's eth0
> 
>  
> 
>     Did work:
> 
>     devices:
>       default:
>         ipv4.address: 192.168.0.36/24 <http://192.168.0.36/24>
>         name: eth0
>         nictype: bridged
>         parent: br0
>         type: nic
> 
> 
> This is probably where you don't setup any IP configuration on the
> container side, so it continue to use whatever address assigned by lxd
> when the container started. For this type of setup though, I recommend
> to NOT rely on lxc config file, but rather set it up directly in the
> container OS.
> 
> -- 
> Fajar
> 
> 
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