FortiGate 300E (Interface speed issue)

[chekidorje]

Hellow

I am having the problem with FortiGate interface speed. My FortiGate is in TP mode and installed in between router and Core switch (both are 1 Gig interface). In order to communicate with router and core Switch, I have to change FortiGate or router and switch interface speed to 100-full. if I keep the same interface speed (auto-negotiation) it won't work. 

Is there any solutions to make 1gig interface speed (router=>FortiGate=>CoreSwitch) and make it work.

Thanks 

Best regards

CD

[connorpm]

I have not seen this issue before but can you provide the router and switch port configs  this sounds like a negotiation issue. 

[rwpatterson]

If both sides are configures to 1000/full, there should be no issues. Auto should never be used on gateway gear.

[chekidorje]

Thanks for your response.

Here is my attached router and switch config.

[chekidorje]

HIrwpatterson

I cannot change the FortiGate interface to 1000-full, I have to make it auto then only it flows 1000-full but no communication happens between Router=> FW=>SW.