# External Provider

You can use *netlab* to create addressing plans and device configurations for a hardware lab **as long as the topology file contains an accurate description of the hardware lab**. 

You can use any device supported by *netlab* with the **external** provider, but you might have to customize the lab topology file -- hardware devices might use:

* Preconfigured management IPv4/IPv6 addresses
* Interface names different from names used by virtual devices
* Different access credentials.

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## Static Management IP Addresses

To specify a static management IPv4/IPv6 address for a lab device, set **mgmt.ipv4** or **mgmt.ipv6** node parameter. To set the management interface name, use **mgmt.ifname** parameter:

* You SHOULD set static management IPv4/IPv6 addresses for all devices in your hardware lab.
* You don't have to set the management interface names for most devices -- management interfaces are usually not configured during the initial device configuration process.

Example:

```
nodes:
  r1:
    mgmt.ipv4: 10.20.30.50
    mgmt.ifname: ether9
```

## Setting Interface Names

*netlab* creates device interface names based on the naming conventions used by virtual devices. If your hardware devices use the same interface names, **and if your lab topology lists links in just the right order** to generate the desired device interface names, you don't have to specify interface names in the lab topology. In most other cases, you REALLY SHOULD specify interface names using **ifname** interface (node-to-link connection) attribute.

Example:

```
links:
- r1:
    ifname: sfp-1
  r2:
    ifname: GigabitEthernet0/3
```

## Access Credentials

It's STRONGLY RECOMMENDED to use usernames and passwords hardcoded into *netlab* with hardware devices (see **devices** section of [topology-defaults.yml](https://github.com/ipspace/netlab/blob/master/netsim/topology-defaults.yml) for more details).

Access credentials are stored in Ansible group variables and derived from the **group_vars** section of device defaults.
To change access credentials for a device type, set the `defaults.devices.<device>.group_vars.ansible_user` and `defaults.devices.<device>.group_vars.ansible_ssh_pass` parameters.

You can also change the access credentials for individual nodes -- set **ansible_user** or **ansible_ssh_pass** node parameters, for example:

```
nodes:
  r1:
    mgmt.ipv4: 10.20.30.50
    mgmt.ifname: ether9
    ansible_user: Vagrant
    ansible_ssh_pass: "vagrant!"
```