openstack-ansible/doc/source/install-guide/ops-troubleshooting-containernetworking.rst

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Container networking issues

All LXC containers on the host have two virtual ethernet interfaces:

• eth0 in the container connects to lxcbr0 on the host
• eth1 in the container connects to br-mgmt on the host

Note

Some containers, such as cinder, glance, neutron_agents, and swift_proxy, have more than two interfaces to support their functions.`

Predictable interface naming

On the host, all virtual ethernet devices are named based on their container as well as the name of the interface inside the container:

${CONTAINER_UNIQUE_ID}_${NETWORK_DEVICE_NAME}

As an example, an all-in-one (AIO) build might provide a utility container called aio1_utility_container-d13b7132. That container will have two network interfaces: d13b7132_eth0 and d13b7132_eth1.

Another option would be to use LXC's tools to retrieve information about the utility container:

# lxc-info -n aio1_utility_container-d13b7132

Name:           aio1_utility_container-d13b7132
State:          RUNNING
PID:            8245
IP:             10.0.3.201
IP:             172.29.237.204
CPU use:        79.18 seconds
BlkIO use:      678.26 MiB
Memory use:     613.33 MiB
KMem use:       0 bytes
Link:           d13b7132_eth0
 TX bytes:      743.48 KiB
 RX bytes:      88.78 MiB
 Total bytes:   89.51 MiB
Link:           d13b7132_eth1
 TX bytes:      412.42 KiB
 RX bytes:      17.32 MiB
 Total bytes:   17.73 MiB

The Link: lines will show the network interfaces that are attached to the utility container.

Reviewing container networking traffic

You can dump traffic on the br-mgmt bridge with tcpdump to see all communications between various containers, but you can narrow your focus by running tcpdump only on the network interfaces of the containers which are experiencing a problem.

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