trying to access the fortigate internally

[chanklish]

hello

I am trying to connect to the fortigate internally but everytime i connect it to my network , my connection is out 

i want to be able to access it from 192.168.20.0/24
i tried putting ip from this subnet on the mgmt or lan2 and connect it to the core switch i have , but the internet is gone from computers connected to this subnet ( but i am able to receive an ip from my dhcp router so connection between fortigate->switch-> router is working 

removing the cable from the switch , internet work .. i believe maybe i have a loop 

Static routes from the fortigate (10.77.77.2 is my main router - same as dhcp ) - it has a route 0.0 .0. 0 / 0 to 10.77.77.1 ( lan switch in fortigate )

[chanklish]

there was no internet before the fortigate..new installation 

everything on the router goes to the fortigate then the internet ....so i suppose adding another cable to this router is creating a loop maybe (2 cables going to lan but with different ip)

[gfleming]

This is very confusing. You previously said " but the problem is that internet goes offline on the computer when i connect the fortigate lan to the router ". This implies you had working internet before plugging in the fortigate.

Can you please explain this better.

[saneeshpv_FTNT]

As gfleming said you are making this so complicated. You have your PC in subnet 192.169.20.x and its default GW is on the Router. Router has a default route to FGT LAN IP 10.77.77.1 and your internet is working fine which means policy and NAT is fine. So in this case as gfleming already stated, you just need to enable HTTPS and SSH on your LAN interface on the FGT so that you can manage your FGT from 192.168.20.x and also see if you have defined any Trusted host IP under -System-> Administrators" for access control.

[chanklish]

i enabled the HTTPS and SSH on the LAN and logged in using the 10.77.77.1 from my pc 

thank you