netgen

The swiss army knife of network simulation.

netgen is a low footprint tool using linux namespaces to set up a topology of virtual nodes, network interfaces and switches on your local machine. There is a strong builtin support for FRR which can be configured to run on such a virtual node to simulate routing scenarios. Nevertheless netgen follows a plugin architecture and can be used in many different ways, not necessarily related to FRR.

Installation

Install ruby:

Debian-based Linux distributions:

$ apt-get install ruby ruby-dev

RHEL/Fedora-based Linux distributions:

$ yum install ruby ruby-devel

Install the bundler gem (version 1.15 is needed):

$ gem install bundler -v 1.15
$ bundle _1.15_ install

If you are getting timeouts you might have run into an IPv6 issue. On systemd enabled systems you can use

$ sysctl -w net.ipv6.conf.all.disable_ipv6=1
$ sysctl -w net.ipv6.conf.default.disable_ipv6=1

to disable IPv6.

Download and install netgen:

$ git clone https://github.com/rwestphal/netgen.git
$ cd netgen/
$ bundle install
$ bundle exec rake install

Usage

Two configuration files are needed to set up a netgen topology:

1. The netgen configuration config.yml
2. The topology configuration, see e.g. /examples/frr-isis-tutorial.yml

Then netgen can be started like this (using superuser permissions):

$ netgen -f config.yml topology.yml

By default the config.yml is taken from the current directory, so a 'quick' way to get something running would be for example:

$ netgen examples/frr-isis-tutorial.yml

If this doesn't work out, make sure you have FRR installed and executables (like zebra) in your $PATH.

netgen follows a plugin architecture and those plugins can be configured in the config.yml. The most important plugin here is frr. Have a look into the provided example config.yml to get an overview. By default netgen stores all information in /tmp/netgen including PCAP files for all interfaces and FRR logs from every node. This makes introspection quite easy.

Working with Nodes

There are two ways of working on the nodes which are configured in the topology file, the tmux plugin or netgen-exec (again, you need superuser permission).

By default a tmux session is created an accessible via:

$ /tmp/netgen/tmux.sh

Here you will see by default one tab per configured node. The tabs are named after the node name.

Run a program directly using netgen-exec on a given node:

$ netgen-exec rt0 vtysh
$ netgen-exec rt1 bash
$ netgen-exec rt1 ifconfig

Topology Configuration

There is an example topology configuration at /examples/frr-isis-tutorial.yml which will teach you how to

• setup a node (with and without FRR)
• setup interfaces
• setup switches
• use the frr plugin
• use the shell plugin
• introspect interfaces and nodes

What is not further explained here are networking and FRR related configuration basics. The example is about IS-IS and it is assumed that the reader is somewhat familiar with it. FRR configuration docu is available here.

The example can be run using:

$ netgen examples/frr-isis-tutorial.yml

As explained above you can use tmux or netgen-exec to perform e.g. a ping test on the src node to check if the dst node is available by executing ping 9.9.9.2. It might take a minute until this test is successful because IS-IS distribution was not established yet.

Note that by default the tmux session, PCAPs, logs etc. are available in /tmp/netgen:

$ ls /tmp/netgen/
frrlogs/  mounts/   pcaps/    perf/     pids.yml  tmux.sh

$ ls /tmp/netgen/pcaps/
dst/ rt1/ rt2/ rt3/ rt4/ rt5/ rt6/ src/ sw1/

Basic Configuration Structure

routers:

  some_node:
    links:
      some_interface:
        peer: [some_other_node, some_other_interface]
        ipv4: 1.2.3.4/32
        [further interface configuration]
    frr:
      zebra:
        run: yes
        config:
        [further zebra config]
      [further FRR config]
    shell: |
      echo "Hello World!"
      [further shell commands executed at node start]
    some_other_plugin:
      [further plugin configuration]
    [further node configuration]

  some_other_node
    [node configuration]

switches:
  sw1:
    links:
      some_switch_interface:
        peer: [peer-interface1, peer-interface2]
      [further interfaces]
  [further switch nodes]

frr:
  perf: yes
  valgrind: yes
  base-configs:
    all: |
      hostname %{node}
      password 12345
      [further configuration for all FRR nodes]
    zebra: |
      debug zebra kernel
      [further zebra configuration for all nodes]
    [further configuration for other daemons on all nodes]

There is one very important thing here to remember: many configuration parts are forwarded to FRR and its daemons as literal blocks and those blocks must be preserved in YAML e.g. using the | sign. This also means that newlines must be taken special care of using ! as connector in the following sense:

config: |
  some_config:
    [some sub configuration]
  !
  some_other_config:
    [some other sub configuration]

Development

TODO

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/rwestphal/netgen.