Design a Topology

Design a Topology Overview

The design phase is the initial step in creating a network topology. During the design phase, you will perform the tasks described in the following sections.

Topology Nodes and Connections

The topology you design consists of nodes and connection functions. See Navigating Within the Cisco Modeling Labs Client for additional information about how to select and edit nodes and connection functions.

Topology Nodes

Table 1 Node Subtypes

Node Name

Node Type

Cisco IOSv

Router node. Runs a Cisco IOS operating system.

Cisco IOSvL2

Router node. Runs a Cisco IOS Layer 2 operating system.

Server

Server node. Runs a Linux operating system.

Cisco IOS XRv

Router node. Runs a Cisco IOS XR operating system.

Cisco IOS XRv 9000

Router node. Runs a Cisco IOS XR 9000 operating system. (Available separately.)

Cisco CSR1000v

Router node. Runs a Cisco CSR 1000 operating system. (Available separately.)

Cisco ASAv

Router node. Runs a Cisco ASAv operating system.

Cisco NX-OSv 9000

Router node. Runs a Cisco Nx-OS 9000 operating system.

A node subtype is a virtual machine that runs on top of OpenStack, which itself is running in a Linux virtual machine that is running on top of VMware software. Because the node is virtual, specific hardware is not emulated. For example, there are no power supplies, no fans, no ASICs, and no physical interfaces. For all router nodes, the interface type is a Gigabit Ethernet network interface. A server node has an Ethernet network interface.

You can choose an image and image flavor for each node type. See the User Workspace Management chapter in the Cisco Modeling Labs Corporate Edition System Administrator Installation Guide, Release 1.3 for information on how to access the VM Image and the VM Flavor choices. In most cases, you need not select an image and flavor. By default, the node subtype is associated with an image and flavor that runs with the topology.

Table 2 Node VM Images

VM Image Name

Used For

server

Server node

CSR1000v

Cisco CSR1000 node

IOSv

Cisco IOS node

IOSvL2

Cisco IOS Layer 2 node

IOS XRv

Cisco IOS XR node

IOS XRv 9000

Cisco IOS XR 9000 node

AVAv

Cisco AVAv node

Nx-OSv 9000

Cisco NX-OSv 9000 node

Table 3 Node VM Flavors

VM Flavor Name

Used For

m1_tiny

Linux server

m1_small

Linux server

m1_medium

Linux server

m1_large

Linux server

m1_xlarge

Linux server

server

Linux server

CSR1000v

Cisco CSR 1000 node

IOS XRv

Cisco IOS XR node

IOS XRv 9000

Cisco IOS XR 9000 node

IOSv

Cisco IOS node

IOSvL2

Cisco IOS Layer 2 node

AVAv

Cisco AVA node

NX-OSv 9000

Cisco NX-OS 9000 node

Each Linux flavor provides a different amount of memory and CPU allocated to the server.

Connection Functions

Cisco Modeling Labs provides the connection functions shown in the following table.

Table 4  Connection Functions
Connection Type Description
Connection Creates a connection between two interfaces. Interfaces are created in the node to support a connection. Any unused interfaces present are automatically assigned. All the interfaces in router nodes are represented as Gigabit Ethernet interfaces. Multiple parallel connections are supported.
External Router Creates an external router connection point.

When the external router is used in conjunction with a Layer 2 External (Flat) network and IOSv instances, AutoNetkit is able to configure an L2TPv3 tunnel to connect simulations to remote devices in a transparent manner.

Layer 3 External (SNAT) Creates a Layer 3 external connection point using static network address translation (SNAT). This external connection point allows connections outside of Cisco Modeling Labs to connect to the topology.
Layer 2 External (Flat) Creates a Layer 2 external connection point using FLAT. This external connection point allows connections outside of Cisco Modeling Labs to connect to the topology.

Create a Topology

Before You Begin

A topology project folder must exist.

There are several methods for creating a topology. These are discussed in the following sections.

Method 1: Create a Topology from the Menu Bar

    Step 1   Select a topology project folder.
    Step 2   Enter a filename, ensuring that it ends with the extension .virl.
    Step 3   Click Finish. A filename .virl topology file is created in the selected project folder.

    Method 2: Create a Topology from the Projects View

      Step 1   Right-click Projects view.
      Step 2   Choose New > Topology.
      Step 3   Select a topology project folder.
      Step 4   Enter a filename, ensuring that it ends with the extension .virl.
      Step 5   Click Finish. A filename .virl topology file is created in the selected project folder.

      Method 3: Create a Topology from the Toolbar

        Step 1   Click the New Topology File icon in the toolbar.
        Step 2   Select a topology project folder.
        Step 3   Enter a filename, ensuring that it ends with the extension .virl.
        Step 4   Click Finish. A filename .virl file is created in the selected project folder.
        What to Do Next

        Place the nodes.

        Place the Nodes on the Canvas

        Before You Begin
        • A topology file must exist.
        • The topology file must be open and the canvas visible in the Topology Editor.
          Step 1   Click a node type, which is under the Nodes heading in the Palette view.
          Step 2   Click the canvas at each point where you want to place a node. You can also drag the nodes on the canvas to position them. You can then arrange the nodes using several methods:

          • Use Shift-click to select two or more nodes. Alternatively, click and drag a selection box around two or more nodes. You can also use Ctrl-click (Windows) or Cmd-click (OS X) to toggle between node selections.

          • From the menu bar, use Edit > Grid > Distribute Nodes to arrange the selected nodes vertically, horizontally, or to distribute them on a grid.
            Note    The grid is determined dynamically, based on the selected nodes.
          What to Do Next

          Create connections and interfaces.

          Create Connections and Interfaces

          Before You Begin

          Nodes must be in place on the canvas of the Topology Editor.

            Step 1   Click Connection in the Tools view.
            Step 2   Click the first node.
            Step 3   Click the next node to create the connection.
            Note    When you connect two nodes, the interfaces are created and named automatically when you choose File > Preferences > Topology Editor > Associate new connection with interfaces silently check box. You can view the node interfaces when you double-click the node.
            Step 4   Repeat Step 2 and Step 3 until all the connections are in place.
            Tip    You can create multiple parallel connections between two nodes. When a connection is selected, the Topology Editor shows the connection end points and double-clicking a node shows the nodes involved in the connection, all of the interfaces on those nodes, and all the connections between those nodes.
            Note    Choose File > Export > Export Topology Diagram to Image to capture an image of the current topology on the canvas.

            Use Unmanaged Switches

            Users have the choice to use either an unmanaged switch or Cisco IOSv layer 2 to provide a switching service. Unmanaged switches are used in place of the multipoint connection which was available in previous versions of Cisco Modeling Labs. For example, in the following figure there are 3 IOSv instances connected to an unmanaged switch. Each of the interfaces on iosv-1, iosv-2, and iosv-3 appear to be on the same subnet for point to point communication through the unmanaged switch.
            Figure 1. Using an Unmanaged Switch in a Simple Topology



            Unmanaged switch instances use the underlying Linux bridge process running under OpenStack control to provide this connectivity between the various virtual machines. It is a transparent switch.
            Before You Begin

            A topology file with the extension .virl must exist. Router nodes or server nodes are placed on the canvas. Optionally, connections may exist between nodes.

              Step 1   In the Nodes view, click Unmanaged Switch.
              Step 2   Click the area on the canvas where you want the unmanaged switch to appear.
              Step 3   In the Tool view, click Connect.
              Step 4   On the canvas, click the unmanaged switch node then click an end node. A connection appears. Continue clicking unmanaged switch-node combinations until all connections are made.
              Figure 2. Using an Unmanaged Switch



              The Cisco IOSvL2 Switch Image

              The Cisco IOSvL2 switch image is a virtual machine like Cisco IOSv, Cisco IOS XRv, and so on. It runs and is configured in the same way as all other virtual machines. It runs a Cisco IOSv 15.2 switch image.

              Note
              All Cisco IOSvL2 switch images in a topology are counted against the licensed node limit.

              A Cisco IOSvL2 switch image provides sixteen Gigabit Ethernet interfaces, reserving interface Gi0/0 for OOB management. It can be configured manually or using AutoNetkit.

              Cisco IOSvL2 switch instances can operate in:

              • Layer 2 mode

              • Layer 3 mode

              By default the instances operate in layer 3 mode. However, the primary use of the Cisco IOSvL2 switch image is for switching purposes.

              Any routers set up to connect to the Cisco IOSvL2 switch will be in switchport access mode. By default, all routers are placed in VLAN 2. You can specify which VLAN to place a port in by setting a VLAN attribute on the router interface. See Assign VLANs for details on how to do this.

              Switch to switch connections configured using AutoNetkit are by default set to operate as an 802.1q trunk.

              Use the Cisco IOSvL2 Switch Image

                Step 1   In the Nodes view, click IOSvL2.
                Step 2   Click the canvas at each point where you want to place an IOSvL2 node. You can also drag the nodes on the canvas to position them.
                Step 3   Add additional node types as required.
                Step 4   Use the Connect tool to create connections between the nodes.
                Step 5   To specify which VLAN to place a port in, select the interface for the host or router by double-clicking the applicable node.
                Step 6   Under Properties > AutoNetkit, enter a value for the VLAN field, as shown.
                Figure 3. Setting the VLAN Attribute



                Step 7   From the toolbar, click Build Initial Configurations to generate a configuration for the topology using AutoNetkit. When prompted to open AutoNetkit visualization, click Yes. AutoNetkit visualization for the topology opens in a browser window.
                Figure 4. AutoNetkit Visualization



                Step 8   To view all broadcast domains that are enabled, select layer2_conn from the phy drop-down list. For example, hovering over server-2 in this example shows the routers and servers that are in the same VLAN. All other devices are greyed out.
                Figure 5. Layer 2 Connectivity



                Selecting layer2 from the phy drop-down list shows the switches representing the VLANs in place.
                Figure 6. Layer 2 Switches



                Step 9   In the Cisco Modeling Labs client, click Launch Simulation to start the simulation. The simulation starts and is visible in the Simulations view.

                Figure 7. Simulation with Cisco IOSvL2 Switch Image



                Docker Container Support

                Cisco Modeling Labs provides the ability to integrate Docker images into Cisco Modeling Labs topologies.

                Users are able to select docker images from public repositories (such as hub.docker.com) or private repositories. Once downloaded to your Cisco Modeling Labs server, you are able to design a network topology that will include your docker image.

                In Cisco Modeling Labs, docker functionality is placed inside another virtual machine, CoreOS; which acts as a host for running docker instances. This is done for two reasons, for security and to constrain and restrict how many instances you have running by putting in place memory controls around the resources utilizations of the various docker instances.


                Note
                You must install the CoreOS virtual machine image. This is available for installation from the Cisco Modeling Labs FileExchange. Please contact cml-info@cisco.com if you require access.

                You can have many docker instances but you need to be careful with the amount of memory that docker instances require. Understand that CoreOS is running docker services as well as the docker instances themselves. There is a limit of 22 docker instances running at any one time. This limit is set by the number of interfaces that the KVM supports.

                Basic configuration information (interface and routing details) are provided by AutoNetkit using the build initial configurations function. As part of the simulation launch, the CoreOS virtual machine is spun up and the docker instance started within it. The docker instance will appear as if it were directly connected to the other nodes within your simulation. The neighboring devices are unaware of the presence of the CoreOS VM that is hosting the docker instances. Each link that is created in the topology design results in an external tap interface being created on the CoreOS instance. The CoreOS VM is configured to run with 2Gb RAM and 2vCPUs. If the amount of memory is insufficient, it can be adjusted using the Node Resources/Flavors function in the User Workspace Management interface.

                There are thousands of docker images available on public repositories. However, not all images will run on Cisco Modeling Labs (or any other docker deployment), so care must be taken when selecting the image.

                Using Integrated Docker Containers in Cisco Modeling Labs Topologies

                To use integrated docker containers in your topologies, complete the following steps.

                  Step 1   Download the docker image to the Cisco Modeling Labs server.
                  Step 2   In the User Workspace Management interface, the list of available subtypes is accessed using Node Resources > Subtypes as shown.
                  Figure 8. List of Available Subtypes



                  For each docker type that is added, you need to create a subtype using the Specialize option to clone the template provided.

                  Figure 9. Create a Subtype Docker Container



                  The required fields to complete are:

                  • Name of plugin

                  • Name of Default Image

                  • Arguments for LXc template; docker run CMD

                  Click Create.

                  The newly created subtype is displayed in the Subtypes list.
                  Figure 10. Docker Subtype Created



                  Step 3   Under Node Resources > Containers > Docker Images, click Add.

                  Browse the docker repository and search for the applicable image, for example, coreos/apache. Select the option and note down the applicable Docker Pull Command, eg. docker pull coreos/apache.

                  Step 4   In the Create Docker Image page, select the newly created docker subtype from the drop-down list.
                  Figure 11. Create Docker Image



                  In the Image Name field, enter the docker pull command noted earlier. Click Create Image.

                  The content is now downloaded. The new docker image is displayed in the Docker Images list.
                  Step 5   To add the docker image for use in Cisco modeling Labs topologies, open the Cisco modeling Labs client.
                  Step 6   Choose File > Preferences > Node Subtypes and click Fetch from Server. The newly created docker image is displayed in the Node Subtypes list. Additionally, the docker image icon is also available from the Topology Palette for use in topology design.