{"id":1024,"date":"2016-11-02T00:21:59","date_gmt":"2016-11-02T05:21:59","guid":{"rendered":"https:\/\/www.softwareab.net\/wordpress\/?p=1024"},"modified":"2016-11-02T18:37:13","modified_gmt":"2016-11-02T23:37:13","slug":"docker-linux-networking-custom-interfaces","status":"publish","type":"post","link":"https:\/\/www.softwareab.net\/wordpress\/docker-linux-networking-custom-interfaces\/","title":{"rendered":"Docker and Linux Networking: Custom Interfaces!"},"content":{"rendered":"

Hi All. Today my goal was to build on a previous post I wrote on Default Routing, RIP v2, and VMware Workstation NICs<\/a>. The problem? I am running on AWS EC2<\/a> so nested virtualization options are lacking (Ravello Systems has a solution<\/a>, but I didn’t want yet-another-layer in between my CloudFormation templates and my EC2 VMs). Therefore, Docker<\/a> to the rescue – I can run all the containers on straight EC2 VMs all I want.<\/p>\n

However – my current use case is to build a “sysadmin testing lab” on EC2 that includes some Cisco router emulators (see Dynagen \/ Dynamips). To do this, I want to hook some of my Docker containers in with my router emulators so I can support the following network architecture:
\n<\/a><\/p>\n

The drawing is from Chapter 8 of Todd Lammle CCNA Study Guide<\/a> and I figured would be an awesome way to weed out network admin wannabe’s. I’ll just have a router or two fired up, and see if the would-be network admin can answer things like “What does show ip int br<\/code> do?”<\/p>\n

Or – better yet – maybe answer how I built such an environment without<\/strong> the use of VirtualBox, VMware Workstation, KVM, or other virtualization tools. In other words, how I can connect my underlying Docker containers on my EC2 instance to the Dynamips emulated routers.<\/p>\n

Plumbing…<\/h2>\n

This article is based on a CentOS 7 minimal EC2 instance with “just-enough” software added to permit me to run Puppet, Docker, and Dynamips\/Dynagen. I’m not going to cover my CloudFormation script (although that would make a great article in and of itself – constructs the networks, IAM policies, auto-scaling groups, launch configurations, and everything and then fires off Puppet to apply policy).<\/p>\n

Instead, we’re going to cover the meat of the article: attaching a customized network interface to a Docker container.<\/p>\n

The underlying principle: veth<\/code> pairs<\/strong>. Before going further, I suggest you read up on veth pairs<\/code>. A good reference is Fun with veth devices, Linux virtual bridges, KVM, VMware \u2013 attach the host and connect bridges via veth<\/a>.<\/p>\n

The Networks – and the “Host” Network!<\/h2>\n

First – remember that we are emulating a set of networks, so here are the network mappings:<\/p>\n