Technical Tip: FortiGate SDWAN overlapping routes

Description

This article describes how to add overlapping routes when using SDWAN in FortiGate for the SD-WAN member interface and the non-SDWAN member interface.

Scope

FortiOS.

Solution

Below is an example for a route to 192.168.0.0/16 pointing to the SD-WAN zone. FortiGate allows administrators to configure overlapping routes on SD-WAN members and non-SD-WAN members.

In this example, it is possible to configure a route to 192.168.1.0/24 using the port3 interface (with port3 included in the SD-WAN zone) and the port4 interface (with port4 not included in the SD-WAN zone).

From the CLI:

Ertiga-kvm14 # get router info routing-table all

Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP

O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

V - BGP VPNv4

* - candidate default

Routing table for VRF=0

C 10.47.0.0/20 is directly connected, port2

C 10.47.16.0/20 is directly connected, port3

C 10.47.32.0/20 is directly connected, port1

S 192.168.0.0/16 [1/0] via 10.47.15.254, port2, [1/0]

[1/0] via 10.47.31.254, port3, [1/0]

S 192.168.1.0/24 [10/0] via 10.47.31.254, port3, [1/0] <--- SDWAN member

[10/0] via 10.47.100.254, port4, [1/0] <--- Non-SDWAN member