External Connectivity for Simulations

The External Connector node (ext-conn) can be used to connect one or more simulation nodes to a network outside of the CML virtual environment. This connector can be configured as a Bridge or NAT device. To reduce complexity and overhead, the external connector node provides a single interface for connectivity.

External Connector - Bridge Mode

Bridge mode provides an unrestricted layer-2 connection to networks outside of the CML virtual environment. Standard networking rules apply. You must provide the required networking configuration on all simulation nodes that have been connected to the external network.


Caution

It is possible for you to cause disruption on your real network or to trigger a loss of access to the CML server when you simulate a lab that uses bridge mode on an external connector. For example, ports on IOSv-L2 nodes are L2 by default with PVST STP and auto-negotiation for trunking enabled. If your topology has such an L2 device configured in switch-mode and if one of the switch ports is in the same broadcast domain as the external connector's port, when the L2 port comes up, it will transmit BPDUs that can trigger either an err-disable on an upstream switchport or a spanning tree event that can cause wider network disruption.

In this example, out-of-band (OOB) management connectivity is provided to multiple nodes using a single ext-conn node and leveraging an Unmanaged Switch.

Use Case Provide layer-2 access to the simulation from the external network OOB (out of band) management of simulated devices.
Topology IOSv router connecting an IOSv-L2 switch
Required Nodes

External Connector (×1)

Unmanaged Switch (×1)

IOSv (×1)

IOSvL2(×1)

Procedure

Step 1

Create a new lab in the Lab Manager.

Step 2

Optional: Give the new lab a name. Example: bridge_connector.

Step 3

Click the bridge_connector lab tile to open the Workbench.

Step 4

Drag-and-drop the required nodes onto the topology canvas.
Step 5

Connect ext-connB to unmanaged-switch.

Step 6

Connect the iosv and iosvl2 nodes to unmanaged-switch using gi0/0 to any port on the unmanaged-switch.

Step 7

Select the ext-conn node.

Step 8

Click the Edit Config tab in the bottom pane.

Step 9

Click Bridge in the Edit Config pane to select bridge mode.

Step 10

Press the ESC key to deselect the ext-conn node.

Step 11

Optional: Click the Design tab in the bottom pane.

Step 12

Optional: Click Build Initial Bootstrap Configurations in the Design pane.

This action provides a basic configuration and a system-assigned username and password of cisco/cisco to the Cisco routers in the lab.

Step 13

Click the Simulate tab in the bottom pane.

Step 14

Click Start in the Simulate pane.

The system will start a lab simulation, and the node VMs will start booting.
Step 15

Wait for all nodes to finish booting.

Once all nodes have booted, you still need to configure each node for OOB management. This example will show how to configure basic connectivity using a VRF for management and routing on interface gi0/0.

Step 16

Select the IOSv node.
Step 17

Click the Console tab in the bottom pane.

Step 18

Click the Open Console button in the Console pane.

Step 19

Log in.

Use the credentials that you set in the initial configs for the devices.

Username: cisco
Password: cisco
Step 20

Add a VRF config to the node.

Sample VRF config:

enable
conf t
vrf definition Mgmt-intf
address-family ipv4
int gi0/0
ip address n.n.n.n m.m.m.m (IP address and subnet mask)
exit
ip route vrf Mgmt-intf 0.0.0.0 0.0.0.0 g.g.g.g (source destination gateway)
Step 21

For each node that requires OOB management to the bridged network, add a VRF configuration by repeating the steps from Step 16 to Step 20.

External Connector - NAT Mode

NAT connectivity can be provided to any connected node in the topology using the External Connector node (ext-conn). This connection can be leveraged, for example, to install packages from a Linux repository or other external public or private package repository.

An IP address is dynamically assigned to the connected node using the next available address from the DHCP pool.

Table 1. NAT Network
Network 192.168.255.0 /24
Gateway 192.168.255.1
DHCP Pool 192.168.255.2 - .254

The router and switch used in the following topology example are not required to leverage NAT mode. They are included only for demonstration and to provide a use case reference.

Use Case Provide NAT access to the external network for a Linux server running in a simulation.
Topology IOSv router connecting an IOSv-L2 switch and a Server node connected to an upstream switch and an External Connector node.
Required Nodes

External Connector (×1)

Server (×1)

IOSv (×1)

IOSvL2(×1)


Note

The NAT network is not currently editable. This network is the internal interface of the External Connector and is not exposed to the Workbench. Making the NAT network for the External Connector node configurable via the Workbench is on the CML roadmap and is planned for a future release.

Procedure

Step 1

Create a new lab in the Lab Manager.

Step 2

Optional: Give the new lab a name. Example: nat_connector.

Step 3

Click the nat_connector lab tile to open the Workbench.

Step 4

Drag-and-drop the required nodes onto the topology canvas.
Step 5

Connect ext-conn to server, using eth1.

Step 6

Connect the iosv and iosvl2 nodes to each other using gi0/1.

Step 7

Connect the server and iosvl2 nodes to each other using eth0 to gi1/0.

Step 8

Select the ext-conn node.

Step 9

Click the Edit Config tab in the bottom pane.

Step 10

Click NAT in the Edit Config pane to select NAT mode.

Step 11

Press the ESC key to deselect the ext-conn node.

Step 12

Optional: Click the Design tab in the bottom pane.

Step 13

Optional: Click Build Initial Bootstrap Configurations in the Design pane.

This action provides a basic configuration and a system-assigned username and password of cisco/cisco to the Cisco routers in the lab.

Step 14

Click the Simulate tab in the bottom pane.

Step 15

Click Start in the Simulate pane.

The system will start a lab simulation, and the node VMs will start booting.
Step 16

Wait for all nodes to finish the boot process. Once the server node displays a solid green dot, it is then ready for use. Next, we can verify the NAT connectivity via the External Connector.

Step 17

Select the server node.

Step 18

Click the Console tab in the bottom pane.

Step 19

Click the Open Console button in the Console pane.

Step 20

Log in.

Use the credentials that you set in the initial configs for the devices.

Username: cisco
Password: cisco
Step 21

Run the following command to verify connectivity: ifconfig eth1

The command should return an IP address for subnet 192.168.255.0/24.
Step 22

Run the following command to verify connectivity: netstat -nr

The command should return the default gateway IP of 192.168.255.