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Multi-host docker cluster using OVS/VxLAN on CentOS 7

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Introduction

The community version of RHEL 7; Community Enterprise OS (CentOS) 7 comes with docker 1.8.x. Which does not support multi-host networking as it only support linux bridges. In other words a container on Host A can't talk to a container on Host B. If you have a cluster of 5 nodes then you can't utilize them all.

In this article I'm going to show you how to setup a multi-host docker cluster where containers on different hosts can talk to each other without NATing (Network Address Translation). I'm going to use OpenVSwitch using VxLAN tunnels (or GRE tunnels) both are Linux kernel technologies that are true and tested (they are used in production for years).

The Open Virtual Switch (OVS) is an L2 switch just like physical switch, it has ports where you plug ethernet plugs and it works at MAC address / ARP level to connect them.

Docker 1.9.x shipped in Fedora 23 do support this feature via something called overlay network but even in that case I still prefer O…