[lxc-users] Networking

[Fajar A. Nugraha]

On Thu, Mar 19, 2020 at 12:02 AM Saint Michael <venefax at gmail.com> wrote:
>
> The question is: how do we share the networking from the host to the containers, all of if. each container will use one IP, but they could see all the IPs in the host. This will solve the issue, since a single network interface,  single MAC address, can be associated with hundreds of IP addresses.

If you mean "how can a container has it's own ip on the same network
as the host, while also sharing the hosts's mac address", there are
several ways.

The most obvious one is nat. You NAT each host's IP address to
corresponding vms.


A new-ish (but somewhat cumbersome) method is to use ipvlan:
https://lxd.readthedocs.io/en/latest/instances/#nictype-ipvlan

e.g.:

# lxc config show tiny
...
devices:
  eth0:
    ipv4.address: 10.0.3.101
    name: eth0
    nictype: ipvlan
    parent: eth0
    type: nic

set /etc/resolv.conf on the container manually, and disable network
interface setup inside the container. You'd end up with something like
this inside the container:

tiny:~# ip ad li eth0
10: eth0 at if65: <BROADCAST,MULTICAST,NOARP,UP,LOWER_UP,M-DOWN> mtu 1500
qdisc noqueue state UNKNOWN qlen 1000
...
    inet 10.0.3.101/32 brd 255.255.255.255 scope global eth0
...

tiny:~# ip r
default dev eth0


Other servers on the network will see the container using the host's MAC

# arp -n 10.0.3.162 <=== the host
Address                  HWtype  HWaddress           Flags Mask            Iface
10.0.3.162               ether   00:16:3e:77:1f:92   C                     eth0

# arp -n 10.0.3.101 <=== the container
Address                  HWtype  HWaddress           Flags Mask            Iface
10.0.3.101               ether   00:16:3e:77:1f:92   C                     eth0


if you use plain lxc instead of lxd, look for similar configuration.

-- 
Fajar