Dell Command Line Reference Guide for the S4048–ON System 9.14.2.4

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mtu

Set the link maximum transmission unit (MTU) (frame size) for an Ethernet interface.

Syntax
mtu value

To return to the default MTU value, use the no mtu command.

Parameters
value
Enter a maximum frame size in bytes. The range is from 592 to 9216.
Defaults
1554
Command Modes
INTERFACE
Command History

This guide is platform-specific. For command information about other platforms, see the relevant Dell EMC Networking OS Command Line Reference Guide.

Version
Description
9.10(0.1)
Introduced on the S6010-ON and S4048T-ON.
9.10(0.0)
Introduced on the S3148.
9.10(0.0)
Reduced the maximum size of the maximum transmission unit (MTU) to 9216 bytes on S6000, S6000-ON, S4048-ON, Z9500, and C9010. Introduced on the S6100–ON.
9.8(2.0)
Introduced on the S3100 series.
9.8(1.0)
Introduced on the Z9100–ON.
9.8(0.0P5)
Introduced on the S4048-ON.
9.8(0.0P2)
Introduced on the S3048-ON.
9.7(0.0)
Introduced on the S6000-ON.
9.2(1.0)
Introduced on the Z9500.
9.0.2.0
Introduced on the S6000.
8.3.19.0
Introduced on the S4820T.
8.3.11.1
Introduced on the Z9000.
8.3.7.0
Introduced on the S4810.
8.1.1.0
Introduced on the E-Series.
7.5.1.0
Introduced on the C-Series.
pre-Version 6.2.1.0
Introduced on the E-Series.
Usage Information

If the packet includes a Layer 2 header, the difference between the link MTU and IP MTU (ip mtu command) must be enough bytes to include the Layer 2 header.

When you enter the no mtu command, Dell EMC Networking OS reduces the IP MTU value to 1536 bytes.

Link MTU and IP MTU considerations for port channels and VLANs are as follows.

port channels:
  • All members must have the same link MTU value and the same IP MTU value.
  • The port channel link MTU and IP MTU must be less than or equal to the link MTU and IP MTU values configured on the channel members. For example, if the members have a link MTU of 2100 and an IP MTU 2000, the port channel’s MTU values cannot be higher than 2100 for link MTU or 2000 bytes for IP MTU.
VLANs:
  • All members of a VLAN must have same IP MTU value.
  • Members can have different Link MTU values. Tagged members must have a link MTU 4 bytes higher than untagged members to account for the packet tag.
  • The VLAN link MTU and IP MTU must be less than or equal to the link MTU and IP MTU values configured on the VLAN members. For example, the VLAN contains tagged members with Link MTU of 1522 and IP MTU of 1500 and untagged members with Link MTU of 1518 and IP MTU of 1500. The VLAN’s Link MTU cannot be higher than 1518 bytes and its IP MTU cannot be higher than 1500 bytes.

The following shows the difference between Link MTU and IP MTU.

Layer 2 Overhead
Link MTU and IP MTU Delta
Ethernet (untagged)
18 bytes
VLAN Tag
22 bytes
Untagged Packet with VLAN-Stack Header
22 bytes
Tagged Packet with VLAN-Stack Header
26 bytes

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