lxc-net doesn't like static ip for a bridged container

Question

I've just started to use LXC containers and I found that even if I set a particular ip address on lxc container config file, lxc-ls --fancy shows always another ip, which is pingable and the /etc/network/interfaces settings doesn't override lxc-net settings.

I'm using lxc 2.0.7.

Container configs:

lxc.network.type = veth
lxc.network.hwaddr = 00:1a:b2:ff:62:32
lxc.network.link = lxcbr0
lxc.network.ipv4 = 10.0.3.2/24
lxc.network.ipv4.gateway = 10.0.3.1
lxc.network.flags = up

lxc.rootfs = /var/lib/lxc/debcontainer/rootfs
lxc.rootfs.backend = dir

# Common configuration
lxc.include = /usr/share/lxc/config/debian.common.conf

# Container specific configuration
lxc.tty = 4
lxc.utsname = debcontainer
lxc.arch = amd64

Interfaces configs:

auto eth0

iface eth0 inet static
 address 10.0.3.3
 netmask 255.255.255.0
 gateway 10.0.3.1

Host Interfaces:

eth0      Link encap:Ethernet  HWaddr XX:XX:XX:XX:XX:XX
          ...

lo        Link encap:Local Loopback
          ...

lxcbr0    Link encap:Ethernet  HWaddr 00:16:3e:00:00:00  
          inet addr:10.0.3.1  Bcast:0.0.0.0  Mask:255.255.255.0
          inet6 addr: fe80::216:3eff:fe00:0/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:137 errors:0 dropped:0 overruns:0 frame:0
          TX packets:131 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:16641 (16.2 KiB)  TX bytes:14826 (14.4 KiB)

vethE2RLT9 Link encap:Ethernet  HWaddr fe:66:28:6b:1a:f1  
          inet6 addr: fe80::fc66:28ff:fe6b:1af1/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:137 errors:0 dropped:0 overruns:0 frame:0
          TX packets:161 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:18559 (18.1 KiB)  TX bytes:19428 (18.9 KiB)

Container Configs:

eth0      Link encap:Ethernet  HWaddr 00:1a:b2:ff:62:32  
          inet addr:10.0.3.2  Bcast:255.255.255.255  Mask:255.255.255.255
          inet6 addr: fe80::216:abff:fec4:63ff/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:170 errors:0 dropped:0 overruns:0 frame:0
          TX packets:147 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:20061 (19.5 KiB)  TX bytes:20259 (19.7 KiB)

lo        Link encap:Local Loopback
          ...

lxc-fs Output:

user@debian-8-test:~$ sudo lxc-ls --fancy
NAME         STATE   AUTOSTART GROUPS IPV4                 IPV6 
debcontainer RUNNING 0         -      10.0.3.2, 10.0.3.211 -

Which `lxc` version do you use? – Tombart Feb 06 '17 at 08:28 — Tombart, Feb 06 '17 at 08:28
@Tombart I'm using `lxc` 2.0.7-1. – JumpAlways Feb 06 '17 at 15:56 — JumpAlways, Feb 06 '17 at 15:56

JumpAlways · Accepted Answer · 2017-02-10T03:41:48.333

SOLUTIONS

Edit /etc/default/lxc-net and comment or remove the LXC bridge name, if specified, and the dhcp options:

USE_LXC_BRIDGE="true"
#LXC_BRIDGE="lxcbr0"
LXC_ADDR="10.0.3.1"
LXC_NETMASK="255.255.255.0"
LXC_NETWORK="10.0.3.0/24"
#LXC_DHCP_RANGE="10.0.3.2,10.0.3.254"
#LXC_DHCP_MAX="253"
#LXC_DHCP_CONFILE=""
LXC_DOMAIN=""

Edit /etc/network/interfaces and set static configurations:

auto eth0
iface eth0 inet static
    address 10.0.3.3
    gateway 10.0.3.1
    netmask 255.255.255.0

OR

Set network configs in <container>/config:

lxc.network.type = veth
lxc.network.hwaddr = 00:1a:b2:ff:62:32
lxc.network.link = lxcbr0
lxc.network.ipv4 = 10.0.3.2/24
lxc.network.ipv4.gateway = 10.0.3.1
lxc.network.flags = up

And set manual interface configuration in /etc/network/interfaces:

auto eth0
iface eth0 inet manual

Tombart · Answer 2 · 2017-02-06T23:49:48.080

0

There's probably dnsmasq running for "dynamic" IP assignment, where you'll reserve certain IPs in /etc/lxc/dnsmasq.conf, like:

dhcp-host=web,10.0.3.2

After changing hosts mapping you need to reload dnsmasq:

kill -HUP $(cat /var/run/lxc/dnsmasq.pid)

The dnsmasq is dependent on lxc-net service, you should be able to see the configuration in service status:

systemctl status lxc-net

edited Feb 06 '17 at 23:49

answered Feb 06 '17 at 08:33

Tombart

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Yeah, it should be enough, but I should also be able to use a pre-set configuration in `/etc/network/interfaces` instead of manually modify an interface parameters using `ifconfig`. It seems `interfaces` is just ignored, because no `up/down...` conditions are triggered either. – JumpAlways Feb 06 '17 at 15:54
If I remove the ip settings from the `lxc` container `config`, `lxc-net` gives the container a random ip and then `lxc-ls --fancy` shows multiple ip, the random one and the one I specify in `interfaces`, which are pingable. – JumpAlways Feb 06 '17 at 16:00
@JumpAlways Yep, sorry. Static IP address was the easiest solution for LXC 1. Try setting IP in `dnsmasq.conf` instead. – Tombart Feb 06 '17 at 23:53
Do you mean outside the containers? Because I still can't understand why `interfaces` file seems to be ignored. I managed to assign a unique static ip to the containers limiting the range inside `/etc/default/lxc-net`, but I'd want to learn to use `interfaces` configs. – JumpAlways Feb 08 '17 at 04:17
Limiting DHCP range is not really a solution. Do you have `/etc/lxc/dnsmasq.conf` on your host? – Tombart Feb 08 '17 at 11:03
No, no `dnsmasq.conf`. – JumpAlways Feb 09 '17 at 02:01

lxc-net doesn't like static ip for a bridged container

2 Answers2