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.
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This article summarizes MTU sizes and jumbo frame support on FortiGate devices.

Jumbo frames are packets that are larger than the standard 1500 maximum transmission unit (MTU) size.  Common maximum sizes for jumbo frames include 9000 and 16110 bytes.  Jumbo frames increase data transfer speeds by carrying more data per frame, reducing the overhead from headers.  All routes that carry jumbo frames must have network devices that all support jumbo frames.  Otherwise, the frames will be dropped.

Starting with FortiOS 3.0 MR2, the Fast-Ethernet (100Mbit) and Gigabit-Ethernet (1000Mbit) interfaces of the FortiGate models 300A and upper support jumbo frames with the following details.

Driver, interface, or module name Jumbo Frame support Maximum MTU and FortiGate model examples
FA2/NP1 No 5001FA2 (port 1 and 2), 5005FA2 (ports 7 and 8), 1000AFA2 (port A1 and A2), 3600A (port 9 and 10), 3810A (port 9 and 10).
NP2 based interfaces Yes, since FortiOS v4.0 MR1 8982 bytes on models 310B, 620B, ADM-FB8, ASM-FB4, RTM-XB2, modules.
TG3 based interfaces Platform dependent 1500 bytes on models 620B, 110C, 111C.

9000 bytes on other platforms with tg3.
e1000 interfaces Yes 9126 bytes on models 310B, 310B-DC, 5005, 5001A, 5005FA2.

16110 bytes on all other models.
NP4 based interfaces Yes 9216 bytes - ADM-XD4 / RTM-XD2.
ADM-XE2 and ASM-CE4 Yes 9216 bytes.
FortiController-5208 interfaces Yes 8900 bytes.
FortiController-5103B, FortiController-5903C, FortiController-5913C interfaces Yes 9000 bytes.
5003A Yes 16379 bytes on all interfaces except the Management port (1500 bytes).

See also the related article at the end of this page "How do I adjust maximum transmission unit value?" or the FortiGate Administration Guide available at


How to identify the interface or the driver name

The driver name of an interface can be found with the following CLI command:
FGT# diagnose hardware deviceinfo nic <interface_name>

Some example outputs are given below:

FGT110C # diagnose hardware deviceinfo nic wan1
Description                     Broadcom 570x Tigon3 Ethernet Adapter
Part_Number                     BCM95786T8600
PHY_Device_ID                   5787
Driver_Name                     tg3

FGT310B # diagnose hardware deviceinfo nic port1
Driver Name: NP2
Version: 0.92
Chip Revision: 1
BoardSN: N/A
Module Name: 310B

FGT5005FA2 #  diagnose hardware deviceinfo nic port1
Description         Intel(R) PRO/1000 Network Connection
Driver_Name         e1000

FGT5005FA2 # diagnose hardware deviceinfo nic port8
Chip_Model        FA2/ISCP1B-v3/256MB
FPGA_REV_TAG      06101916
Driver Name       iscp1a/b-DE



Related Articles

Technical Note : How to adjust the Maximum Transmission Unit (MTU) value on a FortiGate interface