Header RSS Feed
 
If you only want to see the articles of a certain category, please click on the desired category below:
ALL Android Backup BSD Database Hacks Hardware Internet Linux Mail MySQL Monitoring Network Personal PHP Proxy Shell Solaris Unix Virtualization VMware Windows Wyse

LXC container in network reachable, but cannot ping between host and container
Friday - Jul 27th 2018 - by - (0 comments)

In the past I've already had some connectivity issues with LXC (see Network connectivity problems when running LXC (with veth) in VMware VM). But today I experienced another kind of problem on a LXC installation on physical servers running Ubuntu 16.04 Xenial.

While network connectivity worked fine from other networks (outside of this LXC host), I was unable to ping between the LXC host and the container.

root@container:~# ping 10.166.102.10
PING 10.166.102.10 (10.166.102.10) 56(84) bytes of data.
From 10.166.102.15 icmp_seq=1 Destination Host Unreachable
From 10.166.102.15 icmp_seq=2 Destination Host Unreachable
From 10.166.102.15 icmp_seq=3 Destination Host Unreachable
From 10.166.102.15 icmp_seq=4 Destination Host Unreachable
From 10.166.102.15 icmp_seq=5 Destination Host Unreachable
From 10.166.102.15 icmp_seq=6 Destination Host Unreachable
^C
--- 10.166.102.10 ping statistics ---
9 packets transmitted, 0 received, +6 errors, 100% packet loss, time 8040ms

root@host:~# ping 10.166.102.15
PING 10.166.102.15 (10.166.102.15) 56(84) bytes of data.
From 10.166.102.10 icmp_seq=1 Destination Host Unreachable
From 10.166.102.10 icmp_seq=2 Destination Host Unreachable
From 10.166.102.10 icmp_seq=3 Destination Host Unreachable
^C
--- 10.166.102.15 ping statistics ---
5 packets transmitted, 0 received, +3 errors, 100% packet loss, time 3999ms

Both host and container are in the same network range and are using the network's central gateway:

root@host:~# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.166.102.1    0.0.0.0         UG    0      0        0 virbr0
10.166.102.0    0.0.0.0         255.255.255.192 U     0      0        0 virbr0

root@container:~# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.166.102.1    0.0.0.0         UG    0      0        0 eth0
10.166.102.0    0.0.0.0         255.255.255.192 U     0      0        0 eth0

Of course the container is using the hosts virbr0 as network link:

root@host:~# cat /var/lib/lxc/container/config  | grep network
lxc.network.type = macvlan
lxc.network.macvlan.mode = bridge
lxc.network.flags = up
lxc.network.link = virbr0
lxc.network.ipv4 = 10.166.102.15/26
lxc.network.ipv4.gateway = 10.166.102.1
lxc.network.hwaddr = 54:52:10:66:12:15

Now I remembered that at home I had a small test-server running which has the same specs as in this setup:

  • The LXC host is running directly on physical hardware
  • The host's primary interface is being re-used as virbr0 (minor difference here: at home it's a single eth0, on this setup its a bonding interface bond0)
  • The OS versions do not differ too much (home: Debian 8, this setup: Ubuntu 16.04)
  • The LXC version is the same (2.0.x)
  • The host and the containers run in the same local network range
  • Both the host and the containers use the central gateway (firewall) as default gateway

But there is one huge difference: At home the pings between the host and the container work, on this setup (as mentioned above) this doesn't work.

The first thing I checked were the virtual bridge settings. And by basically just showing the virbr0 I saw a big difference:

Home:

root@homehost ~ # brctl show
bridge name    bridge id        STP enabled    interfaces
virbr0        8000.1c1b0d6523df    no        eth0
                            veth0-container
                            veth0-container2
                            veth0-container3
                            veth0-container4

This setup:

root@host:~# brctl show
bridge name    bridge id        STP enabled    interfaces
lxdbr0        8000.000000000000    no       
virbr0        8000.a0369ff4d626    no        bond0

Even though several containers are running on this host, they don't show up as listed interfaces under this bridge!

I compared the container network config at home and on this setup and found this:

Home:

root@homehost ~ # cat /var/lib/lxc/invoicing/config | grep network
# networking
lxc.network.type = veth
lxc.network.flags = up
lxc.network.link = virbr0
lxc.network.ipv4 = 192.168.77.173/24
lxc.network.hwaddr = 54:52:00:15:01:73
lxc.network.veth.pair = veth0-container
lxc.network.ipv4.gateway = 192.168.77.1

This setup (again the same output as above):

root@host:~# cat /var/lib/lxc/container/config  | grep network
lxc.network.type = macvlan
lxc.network.macvlan.mode = bridge
lxc.network.flags = up
lxc.network.link = virbr0
lxc.network.ipv4 = 10.166.102.15/26
lxc.network.ipv4.gateway = 10.166.102.1
lxc.network.hwaddr = 54:52:10:66:12:15

The network type is macvlan on this setup. This is because I basically copied the network config from another LXC host in this environment. With the difference that this LXC host was virtual (running in VMware) and not physical. Hence the lxc.network.type was set to macvlan because of the connectivity problems mentioned in article Network connectivity problems when running LXC (with veth) in VMware VM).

As soon as I switched the network.type to veth, the container and the host could ping each other, too. And now the container shows up in brctl:

root@host:~# brctl show
bridge name    bridge id        STP enabled    interfaces
lxdbr0        8000.000000000000    no       
virbr0        8000.a0369ff4d626    no        bond0
                            veth0F7MCH

TL;DR: On LXC hosts running on physical servers/hardware, use veth interfaces. On LXC hosts running themselves as a virtualized host (inside VMware for example), use macvlan interfaces (once again, see Network connectivity problems when running LXC (with veth) in VMware VM).

 

Add a comment

Show form to leave a comment

Comments (newest first):

No comments yet.

Go to Homepage home
Linux Howtos how to's
Monitoring Plugins monitoring plugins
Links links

Valid HTML 4.01 Transitional
Valid CSS!
[Valid RSS]

7059 Days
until Death of Computers
Why?