Troubleshooting Tip: FortiWeb error 'The same Destination has already existed' when adding 0.0.0.0/0
Description
This article describes the routing behavior introduced in FortiWeb v7.0, where the system implements a strict duplicate‑destination check for default routes. Beginning with this release, FortiWeb permits only a single route with destination 0.0.0.0/0 in the routing table. This enforcement applies to both system static routes and HA static routes, ensuring that only one default route is used for outbound forwarding.
DHCP‑learned routes are not subject to this restriction because they are automatically injected and cannot be modified through the FortiWeb interface. When any internal routing context already contains a default route - whether visible in the GUI or not - the system rejects additional attempts to create another 0.0.0.0/0 entry. As a result, administrators may encounter the error 'The same Destination has already existed' even when no default route is displayed in the routing configuration.
Scope
FortiWeb v7.0.x, v8.0.x.
Solution
Duplicate‑destination enforcement (introduced in FortiWeb v7.0).
Starting with FortiWeb v7.0, the routing subsystem enforces a strict duplicate‑destination check. Only one route with the destination 0.0.0.0/0 is permitted. This restriction applies to:
System static routes.
HA static routes.
DHCP‑learned routes are exempt because they are not user‑configurable. If any internal routing context already contains a default route, FortiWeb rejects additional entries, even if the existing route is not displayed in the GUI. For more information on static routes and HA static routes, see Configuring HA settings specifically for active-passive and standard active-active modes.
Routing behavior in Reverse Proxy and multi‑VLAN.
In Reverse Proxy and multi-VLAN setups, FortiWeb handles routing as follows:
Static routes manage general data-plane forwarding.
Policy routes provide granular control for specific services.
Session-based return-path logic applies to inspected Reverse Proxy traffic.
For more details, see Key considerations of network settings in Reverse Proxy mode.
Recommended approach for management-plane isolation.
FortiWeb does not support multiple default routes. For deployments requiring management traffic (FortiGuard, Syslog/SIEM, DNS, NTP, SNMP) to exit via a dedicated interface:
Configure one system default route for production traffic. For details on this, check configuring the network settings.
Use Policy Routes to steer management-plane destinations to the appropriate interface/gateway. For more details, see Technical Tip: HA management interface connectivity setup for Active-Passive mode.
Conclusion:
The error 'The same Destination has already existed' is expected behavior in FortiWeb v7.0 and later. It protects routing table integrity by limiting default routes to a single entry across system and HA tables. Policy Routes should be used for management-plane isolation in multi-interface environments.