Media MTU Sizes by Interface Type

 

The media maximum transmission unit (MTU) is the largest data unit that can be forwarded without fragmentation.

If you change the size of the media MTU, you must ensure that the size is equal to or greater than the sum of the protocol MTU and the encapsulation overhead.

This topic includes following information:

Media MTU Sizes by Interface Type for M5 and M7i Routers with CFEB, M10 and M10i Routers with CFEB, and M20 and M40 Routers

Table 1: Media MTU Sizes by Interface Type for M5 and M7i Routers with CFEB, M10 and M10i Routers with CFEB, and M20 and M40 Routers

Interface Type

Default Media MTU (Bytes)

Maximum MTU (Bytes)

Default IP Protocol MTU (Bytes)

Adaptive Services

(MTU size not configurable)

9192

N/A

N/A

ATM

4482

9192

4470

E1/T1

1504

9192

1500

E3/T3

4474

9192

4470

Fast Ethernet

1514

1533 (4-port)

1532 (8-port)

1532 (12-port)

Note: The maximum MTU for two 100Base-TX Fast Ethernet port FIC is 9192 bytes.

1500 (IPv4), 1497 (ISO)

Gigabit Ethernet

1514

9192

Note: The maximum MTU for one Gigabit Ethernet port FIC is 9192 bytes.

1500 (IPv4), 1497 (ISO)

Serial

1504

9192

1500 (IPv4), 1497 (ISO)

SONET/SDH

4474

9192

4470

Media MTU Sizes by Interface Type for M40e Routers

Table 2: Media MTU Sizes by Interface Type for M40e Routers

Interface Type

Default Media MTU (Bytes)

Maximum MTU (Bytes)

Default IP Protocol MTU (Bytes)

Adaptive Services

(MTU size not configurable)

9192

N/A

N/A

ATM

4482

9192

4470

E1/T1

1504

4500

1500

E3/T3

4474

4500

9192 (4-port)

4470

E3/DS3 IQ

4474

9192

4470

Fast Ethernet

1514

1533

1500 (IPv4), 1497 (ISO)

Gigabit Ethernet

1514

9192 (1- or 2-port)

9192 (4-port)

1500 (IPv4), 1497 (ISO)

Serial

1504

9192

1500 (IPv4), 1497 (ISO)

SONET/SDH

4474

4500 (1-port nonconcatenated)

9192 (4-port OC3)

9192 (4-port OC3c)

4500 (1-port OC12)

4500 (4-port OC12)

4500 (4-port OC12c)

4500 (1-port OC48)

9192 (2-port OC3)

9192 (2-port OC3c)

9192 (1-port OC12c)

9192 (1-port OC48c)

4500 (1-port OC192)

9192 (1-port OC192c)

4470

Media MTU Sizes by Interface Type for M160 Routers

Table 3: Media MTU Sizes by Interface Type for M160 Routers

Interface Type

Default Media MTU (Bytes)

Maximum MTU (Bytes)

Default IP Protocol MTU (Bytes)

Adaptive Services

(MTU size not configurable)

9192

N/A

N/A

ATM

4482

9192

4470

E1/T1

1504

4500

1500

E3/T3

4474

4500

4470

E3/DS3 IQ

4474

9192

4470

Fast Ethernet

1514

1533

1500 (IPv4), 1497 (ISO)

Gigabit Ethernet

1514

9192 (1- or 2-port)

4500 (4-port)

1500 (IPv4), 1497 (ISO)

Serial

1504

9192

1500 (IPv4), 1497 (ISO)

SONET/SDH

4474

4500 (1-port nonconcatenated)

9192 (1- or 2-port)

4500 (4-port)

4470

Media MTU Sizes by Interface Type for M7i Routers with CFEB-E, M10i Routers with CFEB-E, and M320 and M120 Routers

Table 4: Media MTU Sizes by Interface Type for M7i Routers with CFEB-E, M10i Routers with CFEB-E, and M320 and M120 Routers

Interface Type

Default Media MTU (Bytes)

Maximum MTU (Bytes)

Default IP Protocol MTU (Bytes)

ATM2 IQ

4482

9192

4470

Channelized DS3 IQ

4471

4500

4470

Channelized E1 IQ

1504

4500

1500

Channelized OC12 IQ

4474

9192

4470

Channelized STM1 IQ

4474

9192

4470

DS3

4471

4500

4470

E1

1504

4500

1500

E3 IQ

4471

4500

4470

Fast Ethernet

1514

1533 (4-port)

1532 (8-, 12- and 48-port)

1500 (IPv4), 1497 (ISO)

Gigabit Ethernet

1514

9192

1500 (IPv4), 1497 (ISO)

SONET/SDH

4474

9192

4470

T1

1504

4500

1500

CT3 IQ

(excluding M120)

4474

9192

4470

Media MTU Sizes by Interface Type for MX Series Routers

Table 5: Media MTU Sizes by Interface Type for MX Series Routers

Interface Type

Default Media MTU (Bytes)

Maximum MTU (Bytes)

Default IP Protocol MTU (Bytes)

Gigabit Ethernet

1514

  • 9192

  • 9500 (Junos OS 16.1R1 and later releases)

1500 (IPv4), 1488 (MPLS), 1497 (ISO)

10-Gigabit Ethernet

1514

  • 9192

  • 9500 (Junos OS 16.1R1 and later releases)

1500 (IPv4), 1488 (MPLS), 1497 (ISO)

Multi-Rate Ethernet

1514

  • 9192

  • 9500 (Junos OS 16.1R1 and later releases)

1500 (IPv4), 1488 (MPLS), 1497 (ISO)

Tri-Rate Ethernet

1514

  • 9192

  • 9500 (Junos OS 16.1R1 and later releases)

1500 (IPv4), 1488 (MPLS), 1497 (ISO)

Channelized SONET/SDH OC3/STM1 (Multi-Rate)

1514

9192

1500 (IPv4), 1488 (MPLS), 1497 (ISO)

DS3/E3 (Multi-Rate)

1514

9192

1500 (IPv4), 1488 (MPLS), 1497 (ISO)

Note: Starting in Junos OS Release 16.1R1, the MTU size for a media or protocol is increased from 9192 to 9500 for Ethernet interfaces on the following MX Series MPCs:

  • MPC1

  • MPC2

  • MPC2E

  • MPC3E

  • MPC4E

  • MPC5E

  • MPC6E

Note

Starting in Junos OS Release 16.1R1, the MTU size for a media or protocol is increased from 9192 to 9500 for Ethernet interfaces on the following MX Series MPCs:

  • MPC1

  • MPC2

  • MPC2E

  • MPC3E

  • MPC4E

  • MPC5E

  • MPC6E

Starting in Junos OS Release 16.1R1, the MTU size has been increased to 16,000 bytes for certain MPCs. The MTU size for the following MPCs has been increased to 16000 bytes:

  • MPC7E (MPC7E-MRATE and MP7E-10G)

  • MPC8E (MX2K-MPC8E)

  • MPC9E (MX2K-MPC9E)

Starting in Junos OS Release 17.3R1, the MTU size for MX10003 MPC is 16,000 bytes.

Starting in Junos OS Release 17.4R1, the MTU size for MX204 is 16,000 bytes.

Media MTU Sizes by Interface Type for T320 Routers

Table 6: Media MTU Sizes by Interface Type for T320 Routers

Interface Type

Default Media MTU (Bytes)

Maximum MTU (Bytes)

Default IP Protocol MTU (Bytes)

ATM

4482

9192

4470

ATM2 IQ

4482

9192

4470

Channelized OC12 IQ

4474

9192

4470

Channelized STM1 IQ

4474

9192

4470

DS3

4471

4500

4470

Fast Ethernet

1514

1533 (4-port)

1532 (12- and 48-port)

1500 (IPv4), 1497 (ISO)

Gigabit Ethernet

1514

9192

1500 (IPv4), 1497 (ISO)

SONET/SDH

4474

9192

4470

CT3 IQ

4474

9192

4470

Media MTU Sizes by Interface Type for T640 Platforms

Table 7: Media MTU Sizes by Interface Type for T640 Platforms

Interface Type

Default Media MTU (Bytes)

Maximum MTU (Bytes)

Default IP Protocol MTU (Bytes)

ATM2 IQ

4482

9192

4470

48-port Fast Ethernet

1514

1532

1500 (IPv4), 1497 (ISO)

Gigabit Ethernet

1514

9192

1500 (IPv4), 1497 (ISO)

SONET/SDH

4474

9192

4470

CT3 IQ

4474

9192

4470

Media MTU Sizes by Interface Type for EX Series Switches and ACX Series Routers

Table 8: Media MTU Sizes by Interface Type for EX Series Switches and ACX Series Routers

Interface Type

Default Media MTU (Bytes)

Maximum MTU (Bytes)

Default IP Protocol MTU (Bytes)

Gigabit Ethernet

1514

9192

1500 (IPv4), 1497 (ISO)

10-Gigabit Ethernet

1514

9192

1500 (IPv4), 1497 (ISO)

Note

On ACX Series routers, you can configure the protocol MTU by including the mtu statement at the [edit interfaces interface-name unit logical-unit-number family inet] or [edit interfaces interface-name unit logical-unit-number family inet6] hierarchy level.

  • If you configure the protocol MTU at any of these hierarchy levels, the configured value is applied to all families that are configured on the logical interface.

  • If you are configuring the protocol MTU for both inet and inet6 families on the same logical interface, you must configure the same value for both the families. It is not recommended to configure different MTU size values for inet and inet6 families that are configured on the same logical interface.

Media MTU Sizes by Interface Type for PTX Series Packet Transport Routers

Table 9: Media MTU Sizes by Interface Type for PTX Series Packet Transport Routers

Interface Type

Default Media MTU (Bytes)

Maximum MTU (Bytes)

Default IP Protocol MTU (Bytes)

10-Gigabit Ethernet

1514

9500

1500 (IPv4), 1488 (MPLS), 1497 (ISO)

40-Gigabit Ethernet

1514

9500

1500 (IPv4), 1488 (MPLS), 1497 (ISO)

100-Gigabit Ethernet

1514

9500

1500 (IPv4), 1488 (MPLS), 1497 (ISO)

Release History Table
Release
Description
Starting in Junos OS Release 17.4R1, the MTU size for MX204 is 16,000 bytes.
Starting in Junos OS Release 17.3R1, the MTU size for MX10003 MPC is 16,000 bytes.
Starting in Junos OS Release 16.1R1, the MTU size has been increased to 16,000 bytes for certain MPCs.