FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
MTU definition : The largest physical packet size, measured in bytes, that a network can
transmit. Any packets larger than the MTU are divided into smaller
packets before they are sent. The default MTU is 1500 on a FortiGate interface.
To change the MTU on a given interface from the GUI proceed as follows :
Go to System> Network> Interface.
Select the Edit icon for the interface.
Select Override default MTU value (1500).
Enter the new MTU value.
Click OK.
To change the value from the CLI (example on an AMC module - NP2) :
config system interface
edit
"amc-sw1/2"
set vdom
"root"
set
mtu-override enable
set mtu 9000
next
end
See also the related article "Technical Note : Jumbo frames support on FortiGate devices"
