cisco catalyst WS-C3850-24XS 24 port 10g not sync with Firewall

[Subhajit Karmakar]

We have a cisco catalyst WS-C3850-24XS 24 port 10g switch and are unable to connect Fortinet by SEP fiber connection. So basically we want load balancing for ISP, once we connect via VLAN one side gets up & the other side of the port gets down.

[Subhajit Karmakar]

Please help me to fix the issue.

[Kasun Bandara]

what is the fortigate model you are trying? are you have correct SFPs for both sides? and are those are 10G compatible.

[Subhajit Karmakar]

We are using the FortiGate 600E firewall and both sides using the 10G SEP module.

[Subhajit Karmakar]

Please give the solution, what will be the next step we need to do.

Already done-

--We have changed the SEP with the same model.

--Changed fiber cable.

--Checked VLAN that both the side same access port VLAN have been assigned.

[balaji.bandi]

once we connect via VLAN one side gets up & the other side of the port gets down.

Do you have any high-level diagrams and configurations to look

also, post any logs you see on the switch along with show interface x/x

[Subhajit Karmakar]

Still the problem is not resolved.

[Subhajit Karmakar]

Could you please provide any effective solution?

[Kasun Bandara]

make sure you are using correct cables. i guess you are have multi mode SFPs and for that you need to use multimode cables

[Leo Laohoo]

Post the complete output to the command "sh version". 

I want to see what is the exact IOS-XE version as well as the uptime.  
Early releases of 3.X.X and 16.X.X firmware for the 3850 have a long list of bugs affecting the optic ports.  I think there are even some which "crashes" the optic ports after a long uptime so the optics will not get recognized during OID.

[MHM Cisco World]

can you disable the UDLD if you use it and check connection.