# Considerations for Multi-Link system communication

If a remotely managed Firewall has Multi-Link, we recommend adding a primary and a secondary control interface for different ISP connections. Adding a control interface for each ISP connection guarantees connectivity if one of the ISP connections fails.

Make sure that you configure these addresses consistently in the following parts of the configuration:

- For the interface address on the Firewall.
- For the external contact addresses (if applicable).
- In the NAT rules of the Firewall that protects the Security Management Center (SMC) servers (as necessary).

If there is a Multi-Link connection between a Management Server or Log Server and the components that contact them, define a contact address for each network connection. Make sure that your NAT rules translate from each external address to the correct internal address of the SMC server.