# Select NetLinks for Outbound Multi-Link elements

NetLink elements represent ISP connections in Outbound Multi-Link elements.

## Before you begin

You must have NetLink elements that represent your ISP connections.

To use the round trip time NetLink selection method for load balancing, you must configure the probing settings in the Static NetLink or Dynamic NetLink properties.

##

Each NetLink element contains the IP addresses that are used for translating source IP addresses (NAT) so that outgoing connections receive the correct IP address depending on the ISP. This configuration allows the correct routing of the return packets. Each NetLink must have a unique IP address space.

A NetLink can be either static or dynamic. Dynamic NetLinks are supported only for Single Firewalls. In addition, only Dynamic NetLinks are supported if you configure Multi-Link using mobile broadband modems with a Single Firewall. You can use the same NetLink with several firewalls. If you want to use NetLinks with a firewall that has several interfaces with dynamic IP addresses, you must create a separate Dynamic NetLink element for each interface with a dynamic IP address.

For more details about the product and how to configure features, click Help or press F1.

## Steps

1. Select Configuration, then browse to SD-WAN.
2. Browse to Traffic Handlers.
3. Right-click the Outbound Multi-Link element, then select Properties.
4. On the General tab of the Outbound Multi-Link Properties dialog box, click Add.
5. From the NetLink drop-down list, select a NetLink element.
6. From the Network drop-down list, select the Network element that represents the IP address space in the directly connected external network of this network link.
7. In the Selected Range fields, specify the IP address range for dynamic source address translation (NAT) for the internal source IP addresses on this NetLink.
   To define a single IP address, enter the same address in both fields.
8. From the Type drop-down list, select an option to specify how traffic is routed through the NetLink.
9. (Optional) Select the QoS Classes for traffic handled by this NetLink, then click Add.
   You can use the QoS classes to assign the NetLink with or without activating the actual QoS features.
   - You can select the same QoS class for several NetLinks to balance the traffic between the NetLinks. If none of the NetLinks with the appropriate QoS class are available, or if the traffic has not been assigned a QoS class, the traffic is distributed between the NetLinks according to the Method you specify in the Outbound Multi-Link element properties.
   - QoS classes are assigned based on ToS codes in network traffic or in the Access rules. Traffic that has been assigned the selected QoS class uses this NetLink if the NetLink is available.
10. Click OK.
    The NetLink is listed in the Multi-Link Members list.
11. Click OK in the Outbound Multi-Link Properties dialog box.

## Next steps

Continue in one of the following ways:

- (Optional) Define how information about the performance of each NetLink is cached.
- If you manually configured Outbound Multi-Link elements, define NAT rules using the source NAT addressing defined in the Outbound Multi-Link element.

## Outbound Multi-Link Properties dialog box

Use this dialog box to define outbound multi-link properties.

Option | Definition
--- | ---
Name | Specifies the Outbound Multi-Link name.
Category | Categories allow you to flexibly filter your Management Client view.
Select | Opens the Category Selection dialog box.
Comment | An optional comment for your own reference.
Method | Defines the method for link selection. Round Trip Time — The firewall periodically probes the NetLinks to test them for speed and selects the fastest available active NetLink for each new outbound connection. Ratio — Traffic is distributed between all the available active NetLinks according to the relative bandwidth of each NetLink. The NetLink with the highest bandwidth is assigned the largest portion of the traffic.

Option | Definition
--- | ---
Multi-Link Members section
NetLink | Shows the selected Netlink.
Type | Shows whether the Netlink is active or standby. Active — Traffic is routed through the NetLink according to the Method you specify in the Outbound Multi-Link element properties. Standby — Traffic is only routed through the NetLink if all primary (active) NetLinks are unavailable.
Selected Range | Specifies the IP address range for dynamic source address translation (NAT) for the internal source IP addresses on this NetLink.
QoS Classes | Specifies the QoS Classes for traffic handled by the NetLink.
Add | Opens the Multi-Link Member dialog box.
Edit | Opens the Multi-Link Member dialog box for the selected Multi-Link Member.
Remove | Removes the selected Multi-Link Members.

Option | Definition
--- | ---
QoS related settings section
Name | Shows the QoS Class and the Netlink name.
NetLink Role | Shows whether the NetLink is Active or Standy.
Method | The method for link selection. Round Trip Time — The firewall periodically probes the NetLinks to test them for speed and selects the fastest available active NetLink for each new outbound connection. Ratio — Traffic is distributed between all the available active NetLinks according to the relative bandwidth of each NetLink. The NetLink with the highest bandwidth is assigned the largest portion of the traffic. No Load Balancing — Traffic is not balanced between the NetLinks based on the QoS Class.

## Multi-Link Member dialog box

Use this dialog box to select Netlinks for an outbound Multi-Link.

Option | Definition
--- | ---
NetLink | Select the Multi-Link Member NetLink.
Network | Select the Network element that represents the IP address space in the directly connected external network of the network link.
Selected Range | Specifies the IP address range for dynamic source address translation (NAT) for the internal source IP addresses on the NetLink.
Type | Shows whether the Netlink is active or standby. Active — Traffic is routed through the NetLink according to the Method you specify in the Outbound Multi-Link element properties. Standby — Traffic is only routed through the NetLink if all primary (active) NetLinks are unavailable.
QoS Class | Select from the available QoS classes.
Search | Opens a search field for the selected element list.
Up (Backspace) | Returns to the previous folder.
Tools | New — Creates an element of the specified type. Show Deleted Elements — Shows elements that have been moved to the Trash.
Add | Adds the selected QoS Class.
Remove | Removes the selected QoS Class.
QoS Classes | Shows the added QoS Classes.