External Connectivity in Cisco Modeling Labs

External Connectivity to a Node

Depending on how the Cisco Modeling Labs environment has been set up by the system administrator, you may have several ways to externally connect to the nodes in a running simulation.

  1. Bypass the Cisco Modeling Labs client and connect directly to nodes via Out of Band Management IP access using FLAT If enabled by the system administrator, when designing your virtual network, you can specify that you want all nodes to be configured on a reserved management network. All management interfaces are connected to a shared management network segment known as FLAT. This set up will allow you to bypass the Cisco Modeling Labs client and connect directly via Telnet to the nodes.
  2. Connecting to external devices using FLAT Inband access
    When enabled, you can configure your virtual topologies to connect and pass data-plane and control-plane packets to one or more external devices such as routers or traffic generators during a simulation. Since FLAT is a Layer 2 solution, the IP addresses in your topology are reachable externally. The L2 External FLAT tool in the Cisco Modeling Labs client GUI is used to enable this option.

    Note

    Your simulation continues to be driven through the Cisco Modeling Labs client GUI by communicating with the Cisco Modeling Labs server at its IP address that is bound to the relevant management port.

  3. Connecting to external devices using SNAT Inband access As an alternative to Inband access using FLAT, you can set up the Static NAT (SNAT) approach. SNAT is a Layer 3 solution that leverages the use of an internal SNAT router to hide the IP addresses in your topology. This router, internal to the Cisco Modeling Labs server, translates IP addresses inbound and outbound which means that the addressing schemes used on the virtual topology are not propagated outside the virtual network. When configured, an internal and an external address are assigned to the SNAT-assigned interface on the nodes. For example, configuring 10.11.12.1 as the internal address, and mapping it to 172.16.2.51 externally. Traffic sent to 172.16.2.51 will be translated to the correct internal address and presented to the appropriate node.
    The L3 External SNAT tool in the Cisco Modeling Labs client GUI is used to enable this option.

    Note

    Your simulation continues to be driven through the Cisco Modeling Labs client GUI by communicating with the Cisco Modeling Labs server at its IP address that is bound to the relevant management port.

Set Up a FLAT Network for Out of Band (OOB) Management Access

By using an out-of-band (OOB) network connection to the Cisco Modeling Labs simulation, you can connect an external application to the Management port of any router node in the simulated network. All management ports will have an IP address on the OOB network, which is a separate network from the other interface IP addresses.

Before You Begin
  • Ensure that you have installed a third-party application for Telnet connections, such as PuTTY.
  • Ensure that FLAT connectivity has been enabled by the system administrator.
    Step 1   Log in to the Cisco Modeling Labs client.
    Step 2   Verify you have connectivity to the Cisco Modeling Labs server.
    Step 3   Open the Design perspective, if it is not already open.
    Step 4   Open an existing topology or create your network topology. See the section "Create a Topology" for information on how to do this.
    Step 5   Configure the OOB management network.
    1. Click on the Topology Editor canvas.
    2. Choose Properties > Topology.
    3. Locate Management Network and select Shared flat network from the drop-down list.

    The Shared flat network option is what enables the OOB connectivity.

    Step 6   From the toolbar, click the Update Router Configurations tool.

    Note    For the purpose of this task, you may retain the default settings.
    Step 7   After the build phase is completed, initiate the simulation by clicking the Launch Simulation tool in the toolbar, and then change to the Simulation perspective.
    Step 8   (Optional) Enter the ping command on the PC to confirm that the management port on a running node can be reached.
    1. In the Cisco Modeling Labs client simulation, select a router node and display the IP address for its management port. In this example, the IP address for the node management port is 172.16.1.51.

    2. In the PC command window, enter the ping command to target the node management port identified in Step 8a.

    Step 9   (Optional) In the Cisco Modeling Labs client simulation, connect to a console port on a node and confirm the management network IP address exists. Enter the show ip interface brief command to display the IP addresses. For this example, use the IP address 172.16.1.51.

    Step 10   Launch and configure a terminal emulator for a Telnet connection to the node management port. In this example, the PuTTY application is used.
    1. Launch the PuTTY application.
    2. In the PuTTY Configuration window, enter the IP address for a Telnet connection to the management port. In this example, the IP address for the node management port is 172.16.1.51.

    3. When successful, a Telnet window opens and the router console information is displayed.

    Set Up a FLAT Network for Inband Access

    The following procedure describes how to connect your virtual network topology to physical devices that are external to the Cisco Modeling Labs server environment. In this procedure, you will be configuring a FLAT network. A FLAT network uses Layer 2 connectivity in which the IP address information about your virtual network can be viewed externally.

    Before You Begin
    • Ensure that the system administrator has configured the Cisco Modeling Labs server to allow FLAT connections.
    • Ensure that you obtain the IP address of the default gateway from the system administrator.
    • Ensure that you have the IP address of the external device to which the nodes will connect.

    Note
    We recommend that you first draw your intended design, and then label the devices with the appropriate IP addresses.
      Step 1   Log in to the Cisco Modeling Labs client.
      Step 2   Verify you have connectivity to the Cisco Modeling Labs server.
      Step 3   Open the Design perspective, if it is not already open.
      Step 4   Open an existing topology or create your network topology. See the section "Create a Topology" for information on how to do this.
      Step 5   Click on the canvas to open the Topology tab in the Properties view and ensure that Management Network displays <not specified>.
      Step 6   From the Palette view, under General, click the L2 External FLAT tool, and then click the canvas to add one FLAT cloud network icon to each corresponding node icon on the canvas.
      Step 7   From the Palette view, under Tools, click the Connect tool and connect the L2 External FLAT to the desired nodes.

      Note    L2 External FLAT connections can only be assigned to one interface on one node.
      Step 8   From the toolbar, click the Update Router Configurations tool.

      Note    For the purpose of this task, you may retain the default settings.

      The system automatically assigns an IP address to the node interface that is connected to the FLAT cloud during the Simulation phase, not the Build phase.

      Step 9   After the build phase is completed, start the simulation by clicking the Launch Simulation tool in the toolbar, and then change to the Simulation perspective.
      Step 10   Log in to the node that is connected to the FLAT network when its state has changed to ACTIVE.
      Step 11   View the IP address assigned to the FLAT network and determine if it is on the same subnet as the gateway IP address provided by your system administrator. The L2 external address for each node can be viewed from the Simulations view or from each individual node.
      • If yes, continue to Step 12.
      • If no, advise your system administrator and request the correct gateway IP address.
      Step 12   If the external device is on a different subnet, define a default gateway or a broadcast domain that points to the IP address of the gateway that the system administrator supplies.

      Prior to completing this step, if you do a show route, you will see that no default gateway is defined in the node. This is the default set up. This step allows you to inform the node what path to take in order to reach the external environment via the gateway. An alternative to defining a gateway or static route, with IOSv devices, is to enable DHCP on the interface used for external connectivity.

      Note    Not all virtual images support DHCP. Check the supported features for the virtual images to determine which ones do support DHCP.
      Step 13   Test the connection by pinging from the node to the external (physical) device. If required, turn on debug ip icmp or use the tracert command to see the progress through the network.
      Note   

      You must repeat steps 10-13 for each node that is connected to the FLAT network.

      If the ping does not work, confirm with your system administrator that the Cisco Modeling Labs server is configured to support FLAT connectivity and that the gateway IP address you have been provided is correct.

      If these items are correct, ping to each of the key devices in the path to determine where the failure occurs and notify your system administrator of the failure source if it is outside your Cisco Modeling Labs environment.

      Set Up a SNAT Network for Inband Access

      SNAT functionality also allows connected nodes to connect to external devices. Using SNAT, the connectivity occurs at Layer 3 and allows you to hide the simulated virtual network behind a Static NAT address block. The Cisco Modeling Labs server will do a static IP address translation (hence SNAT), translating the private address range allocated to the SNAT ‘inside’ network into the IP network configured for the SNAT ‘outside' network. By default, Cisco Modeling Labs uses an internal gateway function that acts as a SNAT router.

      In the example used here, the iosv-1 GE 0/2 interface has two IP addresses. The addresses on the 172.16.22.0 subnet are reachable from the external devices and will be translated to the internal addresses which are on the 10.11.58.0 network.
      Figure 1. SNAT Functionality



      Using SNAT, the iosv-1 host will have an internal IP address from the 10.11.58.0 infrastructure network on its interface facing the SNAT cloud (10.11.58.2). This will be mapped by the SNAT router for that segment into 172.16.22.53. Assuming that the SNAT interface is connected and there is another host on that segment, such as a gateway, you can now connect to the iosv-1 router via the 172.16.22.53 address.


      Note
      No default gateway is created on the IOSv router. A static route must be added to the iosv-1 router configuration similar to the following example:

      ip route 0.0.0.0 0.0.0.0 10.11.58.1

      where 0.0.0.0 0.0.0.0 refers to all destination IP addresses not found in the routing table and 10.11.58.1 refers to the SNAT router.

      Before You Begin
      • Ensure that the system administrator has configured the Cisco Modeling Labs server to allow SNAT connections.
      • Ensure that the system administrator provides you with the internal and external IP addresses of the SNAT router.
      • Ensure that you have the IP address to the default gateway.
      • Ensure that you have the IP address of the external device to which the nodes will connect.
        Step 1   Log in to the Cisco Modeling Labs client.
        Step 2   Verify you have connectivity to the Cisco Modeling Labs server.
        Step 3   Open the Design perspective, if it is not already open.
        Step 4   Open an existing topology or create your network topology. See the section "Create a Topology" for information on how to do this.
        Step 5   Click on the canvas to open the Topology tab in the Properties view and ensure that Management Network displays <not specified>.
        Step 6   From the Palette view, under General, click the L3 External SNAT tool, and then click the canvas to add one SNAT cloud network icon to each corresponding node icon on the canvas.
        Step 7   From the Palette view, under Tools, click the Connect tool and connect the L3 External SNAT to the desired nodes.

        Note    L3 External SNAT connections can only be assigned to one interface on one node.
        Step 8   From the toolbar, click the Update Router Configurations tool.

        Note    For the purpose of this task, you may retain the default settings.

        The system automatically assigns the internal and external IP addresses to the node interface that is connected to the SNAT cloud during the Simulation phase, not the Build phase. Therefore, no assigned addresses are visible at this point.

        Step 9   After the build phase is completed, start the simulation by clicking the Launch Simulation tool in the toolbar, and then change to the Simulation perspective.
        Step 10   Log in to the node that is connected to the SNAT network when the status of the device has changed to ACTIVE.
        Step 11   Create a static route or define a default gateway for the external connection IP addresses that point to the SNAT router’s internal IP address. For example, if the external connections are part of the subnet 172.16.2.0/24, and the SNAT router’s internal IP address is 10.11.11.1, then the route statement would be:

        ip route 172.16.2.0 255.255.255.0 10.11.11.1

        An alternative to defining a gateway or static route, with IOSv devices, is to enable DHCP on the interface used for external connectivity.

        Note    Not all virtual images support DHCP. Check the supported features for the virtual images to determine which ones do support DHCP.
        Step 12   Test the connection by pinging from the node to the external (physical) device. If required, turn on debug ip icmp or use the tracert command to see the connectivity between the end points.

        If the ping does not work, confirm with your system administrator that the Cisco Modeling Labs server is configured to support SNAT connectivity and that the gateway IP address you have been provided is correct.

        If these items are correct, ping to each of the key devices in the path to determine where the failure occurs and notify your system administrator of the failure source if it is outside your Cisco Modeling Labs environment.