I'm assuming you're trying to do ECMP load balancing between them.
1. Check routing table with "get router info routing-table static". Do you see two default routes existing with the same distance and same priority.
2. What kind of policies do you have? It require two policies to each directions.
3. If the source you're generating the internet-bound traffic from is in the same LAN subnet, it would not work well when the FGT forwarded it to the Cisco because outgoing is 192.168.1.x(source)->192.168.1.10(FGT)->192.168.1.1(Cisco), but for returning the Cisco 192.168.1.1 sends directly to the source 192.168.1.x. The FGT doesn't like it and might block following TCP outgoing packets due to only one way traffic.
You might need to set a VLAN between FGT and Cisco then assign a /30 subnet. Then you can have a proper policy toward the VLAN interface, in addition to the policy toward WAN1.
Made one static route 0.0.0.0/0 with gateway 213.xxx.xxx.xxx which is the next hop in the line which is connected via the cisco router, and an extra static route that for goint to 213.xxx.xxx.xxx ip the gateway is 192.168.1.1 (cisco router lan ip).
Well it seems to work in some computers but not to others. But it must be a case of misconfigured DNS server.. Machines with DHCP work ok, but if they have static ip address they can't use both external lines depending on the fortigate's policies. The static ip pc's can access internet only via the line on WAN port..
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