Technical Tip: Connected route not displayed in routing-table despite interface in different VRF

[sagha]

Description	This article describes the issue where if an interface is getting IP address via DHCP having same subnet as another interface, one of it will not show up in routing table.
Scope	FortiGate, FortiOS.
Solution	Consider having two interfaces configured as follow:  # config system interface     edit "wan1"         set vdom "root"         set vrf 2         set mode dhcp         set type physical         set role wan         set snmp-index 2     next end # config system interface     edit "wan2"         set vdom "root"         set vrf 0         set ip 192.168.1.1 255.255.255.0         set allowaccess ping fgfm         set type physical         set role wan         set snmp-index 2     next end Both interfaces are configured in different VRFs.  wan1 is configured to get IP address via DHCP, while wan2 is configured with a static IP address.  If wan1 ends up receiving the same subnet as wan2, the connected route for one would not show in the routing table, even if it is in different VRFs. # get router info routing-table details Routing table for VRF=0 S* 0.0.0.0/0 [10/0] via 10.1.10.1, internal, [1/0] C 10.1.10.0/24 is directly connected, internal Routing table for VRF=2 S* 0.0.0.0/0 [5/0] via 192.168.1.2, wan1, [1/0] C 192.168.1.0/24 is directly connected, wan1 FortiGate does not allow having to the same subnet on different interfaces with default config. As in the above case, since it was received via DHCP, FortiGate configured it on wan1 but only one route showed up in the routing table as connected. In such cases, it is suggested to configure 'set allow-subnet-overlap'.  # config system settings (settings) # set allow-subnet-overlap enable  (settings) # end This will allow both connected routes in the routing table. # get router info routing-table details Routing table for VRF=0 S* 0.0.0.0/0 [10/0] via 10.1.10.1, internal, [1/0] C 10.1.10.0/24 is directly connected, internal C 192.168.1.0/24 is directly connected, wan2 Routing table for VRF=2 S* 0.0.0.0/0 [5/0] via 192.168.1.2, wan1, [1/0] C 192.168.1.0/24 is directly connected, wan1