What is Cisco VIRL/CML?

At last Cisco Live 2014 (Milan) there was a lab on Cisco VIRL/CML. Only one PC located in the Walk-in-lab room were available to start a VIRL lab, and I couldn’t miss that chance to see what exactly VIRL is. The following post is what I could understand using a VIRL/CML installation during the latest Cisco Live 2014 (Milan).

Disclaimer: in this post there are many "facts" and also many personal "guesses". Things can change, VIRL/CML is not available yet, so everything is evolving.


I can suppose that all readers know what IOU is. By the way let me recap the differences between GNS3, Dynamips, Dynagen, IOU/IOL and iou-web:

  • Dynamips emulates Cisco routers. That’s mean that Dynamips emulates the hardware so a standard IOS can be executed upon it. Dynamips supports both serial and Ethernet interfaces.
  • Dynagen is a text-based front-end for Dynamips.
  • GNS3: is a graphical front-end for Dynamips.
  • IOU (IOS on Unix) emulates Cisco IOS: it’s an executable files which runs under Sparc/Solaris platform. There is also IOL (IOS on Linux) which runs on x86/Linux platform, and there is should another version which runs on Mac OS platform. IOU supports both serial and Ethernet interfaces. There are also IOU/IOL images which supports a limited subset of Layer 2 features.
  • iou-web is a web front-end for IOL (it should works also on Sparc/Solaris, but I never tested it).
  • XR4U (XR for Unix): it should emulates Cisco IOS-XR on Unix/Linux platform, I never seen it runs.

Cisco VIRL (Virtual Internet Routing Lab) is the old name of Cisco Modeling Lab (CML). It’s a graphical front-end for Cisco virtualized appliances. Currently VIRL supports:

  • Cisco CSR1000v: based on IOS-XE it runs 3 GigabitEthernet interfaces and requires about 2Gb of RAM (different versions have different requirements).
  • vIOS: it should requires less resources than CSR1000v, it’s not available for download yet.
  • Cisco IOS XRv: based on IOS-XR it should available for download soon.
  • Ubuntu Linux: it’s a simply Ubuntu Linux Virtual Machine which serves as a server.

All of them are Virtual Machines running x86/x86_64 code.

The main differences between VIRL and IOU are now evident:

  • VIRL is not based on IOU, VIRL needs Virtual Machines;
  • VIRL won’t supports serial interfaces, only Ethernet interfaces will be supported;
  • L2 images are not supported, and maybe they won’t be supported in the future (explained later).

What exactly is Cisco VIRL/CML?

Cisco VIRL/CML is a graphical interface to create and manage labs based on virtual/cloud devices. Technically VIRL/CML is based on:

  • OpenStack and KVM: KVM is the hypervisor who runs Virtual Machines, and OpenStack is the manger.
  • Eclipse; don’t know it’s a Java app or not.
  • Autonetkit: it can automatically allocate IP addresses, configure routing and generate configuration files with templates.

Let’s me clarify: Cisco VIRL/CML is a graphical front-end (like GNS3) which can create labs using x86 images using OpenStack/KVM. It’s faster than Dynamips, more flexible than IOU/IOL, but it supports only L3 Ethernet interfaces. The reason is pretty simple: L2 switches are provided by OpenStack/KVM layer.

My opinion is that L2 interfaces could be supported if a L2 IOS is installed within the OpenStack/KVM suite: like Nexus 1000V is installed within the VMware vSphere suite.

Serial interfaces could be supported also (using classic COM/TTYSx ports), but because VIRL/CML is based on production cloud devices, I suppose we’ll never see L2 or serial interfaces on VIRL/CML.

A good news is that VIRL/CML could support all cloud devices Cisco will make available:

But VIRL/CML could support also:

  • different type of Linux appliances: Ubuntu is already supported;
  • other’s vendor appliances like NetScaler, Imperva, SourceFire…

When VIRL/CML will be released?

Cisco VIRL/CML seems pretty but not completely stable: I can make it crash a couple of time during my test. Rumors say that VIRL/CML will be released not before the end of 2014: someone refers to marketing problems, someone refers to technical problem.

It’s pretty sure that VIRL/CML will be available as OVF/OVA Virtual Machine but also as a bare metal installation (a whole server dedicated to VIRL/CML).

-*Update (2014-04-29):** Cisco Modeling Labs will be released by late Summer 2014:

-*Q.** Is there a hosted or cloud offering? -*A.** No, there is no hosted or cloud offering. -*Q.** How do customers purchase Cisco Modeling Labs? -*A.** The corporate edition will be on the global price list and orderable on the Cisco Commerce Workspace at Cisco.com by late summer 2014.

-*Update (2014-05-22):** Cisco Modeling Labs will be released before the end of July 2014 (thank you, Daniel).


Posted on 03 Feb 2014 by Andrea.
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