icegood
March 27, 2023, 9:57am
1
Hello, i created a small demo to join two containers in vlans over tap0
and i don’t understand why vlan_test1 and vlan_test2 don’t see each other . In case if parent interface is removed i.e. with a fully internal network they see each other.
Is this a bug? I don’t see anything that contradicts to:
# Macvlan Driver
### Overview
The Macvlan driver provides operators the ability to integrate Docker networking in a simple and lightweight fashion into the underlying network. Macvlan is supported by the Linux kernel and is a well known Linux network type. The Macvlan built-in driver does not require any port mapping and supports VLAN trunking (Virtual Local Area Network). VLANs are a traditional method of network virtualization and layer 2 datapath isolation that is prevalent in some form or fashion in most data centers.
The Linux implementation is considered lightweight because it eliminates the need for using a Linux bridge for isolating containers on the Docker host. The VLAN driver requires full access to the underlying host making it suitable for Enterprise data centers that have administrative access to the host.
Instead of attaching container network interfaces to a Docker host Linux bridge for a network, the driver simply connects the container interface to the Docker Host Ethernet interface (or sub-interface). Each network is attached to a unique parent interface. Containers in a network share a common broadcast domain and intra-network connectivity is permitted. Two separate networks will each have a unique parent interface and that parent is what enforces datapath isolation between two networks. In order for inter-network communications to occur, an IP router, external to the Docker host, is required to route between the two networks by hair-pining into the physical network and then back to the Docker host. While hairpinning traffic can be less efficient then east/west traffic staying local to the host, there is often more complexity associated with disaggregating services to the host. It can be practical for some users to leverage existing network services, such firewalls and load balancers that already exist in a data center architecture.
When using traditional Linux bridges there are two common techniques to get traffic out of a container and into the physical network and vice versa. The first method to connect containers to the underlying network is to use Iptable rules which perform a NAT translation from a bridge that represents the Docker network to the physical Ethernet connection such as `eth0`. The upside of Iptables using the Docker built-in bridge driver is that the NIC does not have to be in promiscuous mode. The second bridge driver method is to move a host's external Ethernet connection into the bridge. Moving the host Ethernet connection can at times be unforgiving. Common mistakes such as cutting oneself off from the host, or worse, creating bridging loops that can cripple a VLAN throughout a data center can open a network design up to potential risks as the infrastructure grows.
Connecting containers without any NATing is where the VLAN drivers accel. Rather than having to manage a bridge for each Docker network containers are connected directly to a `parent` interface such as `eth0` that attaches the container to the same broadcast domain as the parent interface. A simple example is if a host's `eth0` is on the network `192.168.1.0/24` with a gateway of `192.168.1.1` then a Macvlan Docker network can start containers on the addresses `192.168.1.2 - 192.168.1.254`. Containers use the same network as the parent `-o parent` that is specified in the `docker network create` command.
There are positive performance implication as a result of bypassing the Linux bridge, along with the simplicity of less moving parts, which is also attractive. Macvlan containers are easy to troubleshoot. The actual MAC and IP address of the container is bridged into the upstream network making a problematic application easy for operators to trace from the network. Existing underlay network management and monitoring tools remain relevant.
### Pre-Requisites
- The examples on this page are all single host and require Docker v1.12 or greater running on Linux.
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I need such configuration as it will be extended with qemu instance with attached tap0 and i want to install vlan here as well