Command Line Reference Guide

562 | Interfaces
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mtu
c e
Set the maximum Link MTU (frame size) for an Ethernet interface.
Syntax
mtu value
To return to the default MTU value, enter no mtu.
Parameters
Defaults
1554
Command Modes
INTERFACE
Command
History
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:
• On C-Series, the IP MTU will get adjusted automatically when the Layer 2 MTU is configured
with the mtu command.
• On the E-Series, you must compensate for a Layer 2 header when configuring IP MTU and link
MTU on an Ethernet interface. Use the ip mtu command.
When you enter the no mtu command, FTOS reduces the IP MTU value to 1536 bytes. On the
E-Series, to return the IP MTU value to the default, enter no ip mtu.
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.
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.
value
Enter a maximum frame size in bytes.
Range: 594 to 9252
Default: 1554
Version 8.1.1.0 Introduced on E-Series ExaScale
Version 7.5.1.0 Introduced on C-Series
pre-Version 6.2.1.0 Introduced for E-Series