FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
This article describes a possible scenario where the user is applying SD-WAN configuration with 3 ISP links.
Scope
FortiGate.
Solution
However, the user is seeing in logs multiple TCP resets from public servers on the internet while traffic is being allowed by the proper SD-WAN rule 3 which has the below settings :
config system sdwan config service edit 3 set name "test" set addr-mode ipv4 set input-device-negate disable set mode load-balance set minimum-sla-meet-members 0 set hash-mode round-robin set role standalone set standalone-action disable set tos 0x00 set tos-mask 0x00 set protocol 0 set route-tag 0 set dst "all" set dst-negate disable set src "Name" set src-negate disable set internet-service disable set dscp-forward disable set dscp-reverse disable config sla edit "SLA" set id 1 next end set priority-members 3 4 5 set status enable set default disable set passive-measurement disable next end
As shown above, the SD-WAN rule has a round-robin hash-mode which may result in public servers receiving the request from different source IPs and eventually will lead to TCP reset.
Change the SD-WAN rule hash mode to be source-ip-based as shown below:
config system sdwan config service edit 3 set hash-mode source-ip-based
