mininet_frr

Free Range Routing (FRR) on Mininet topologies

Purpose

Network emulators enable hands-on learning, experimenting, and testing network protocols on virtual topologies. Mininet uses Linux network namespaces for lightweight emulation of routers, switches, and hosts.

This package uses a simple integration of Mininet and FRR with a variety of example topologies and configurations.

Overview

This repository contains various topologies and configurations that run on a Linux system with FRR and Mininet installed. While not strictly necessary, running Mininet and FRR in a VM is strongly recommended.

To run these examples, clone this repository on an FRR/Mininet system and run the individual Mininet Python scripts.

Topologies

• two_router: 2 routers configured static routes
• ospf: 4 routers running OSPF
• bpg: 4 routers in 3 AS regions running BGP

Running a Toplogy

Each scenario is standalone. To run a scenario, open a Linux terminal and do the following:

• cd into the directory of the example that you want to run.
• configure FRR by running the configure script.
• start the emulation by running the python topology script

Example:

cd two_router
./config_frr.sh
sudo ./mn_topo.py

This starts the mininet emulator and the relevant FRR routing daemons and brings up the mininet command line. Mininet provides access to the linux shell on each emulated node and connectivity tests. To stop the emulation and shutdown the FRR daemons, enter exit or press ^D.

At the mininet> prompt, you can run tests:

For example:

r1 ping r3
pingall

To run Linux shell commands on individual nodes:

r1 ip route

To access the FRR command and configuration shell, run vtysh from a Linux termimal for a specific node: vtysh -N "node name"

Example:

sudo vtysh -N r1
show running-config

Notes

These examples focus on routing protocols and protocol configuration. We use Mininet switches to connect multiple hosts in a subnet. Mininet supports Openflow by running a controller, however these examples do not use Openflow beyond whatever Mininet may be doing (if anything) to make the switches "just work".

The configuration script config_frr.sh creates subdirectories under the FRR configuration, run state, and logging directories and populates the configuration files. Note that any existing configuration files in these directories are erased as new ones are applied. Copy any updated configurations out of /etc/frr/nodename before reconfiguring.

While each of these scenarios "work" in that the routing configuration provides connectivity, they are likely not good examples of how to do things "in the right way". There are improvements that can be made to the FRR configurations.

Requirements

It is assumed that FRR uses the following directories, which are the default under Ubuntu Linux:

• /etc/frr : configuration
• /var/frr : run state
• /usr/lib/frr/frrinit.sh : start script

The scripts in this project create a directory for each routing node under /etc/frr, /var/frr, and /var/log/frr

You can build your own FRR/Mininet VM image. Instructions for building from source can be found at: https://github.com/jmwanderer/mininet_frr/blob/main/make_vm/README.md

Additional Resources

An excellent description of network namespaces and mininet can be found at: Network Emulation using Network Namespaces and Mininet.

Kudos to edoardesd for an answer on Stack Overflow: (mininet) How to create a topology with two routers and their respective hosts

Creating Custom Networks

1. Sketch a network design with IP addresses specified for each interface. Get this right, or nothing will work.
2. Copy or modify an existing example directory
3. Change mn_topo.py and modify the following functions:
   • NetworkTopo: change the hosts, switches, routers, and links
   • Run: startup and shutdown FRR for each virtual router
4. Update config_frr.sh to set the list of virtual routers
5. Create configs for each virtual router:
   • daemons - update to change the routing protocols to be run
   • vtysh.conf - update to contain a unique hostname
   • frr.conf - use vtysh to create your configuration and copy from /etc/frr/node after saving (write) the config.