Description
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 http://docs.fortinet.com
Solution
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
