Underlay

First, you must decide what underlay links you will use to connect all participating sites and the public internet. Do you have multiple internet connections? Or an internet connection and an MPLS link? Or will it be a broadband internet connection and an LTE modem?

How will edge devices get their IP addresses—via DHCP or static configuration? Will there be a need for VLAN tagging? For Link Aggregation?

The same questions also apply to the LAN side. How will the local LAN network connect to the edge device? Are there any additional services needed. For example, will the edge device act as a DHCP server for the local network?

Since all edge devices are full-featured FortiGate devices, the range of possibilities is extensive. While each site can, in principle, be designed and configured differently from the others, we highly recommend defining a limited number of groups of sites with identical configurations within each group. This will simplify provisioning and the operation of your SD-WAN solution.