Reference Guide

ip mtu
Set the IP MTU (frame size) of the packet the RPM transmits for the line card interface. If the packet must be
fragmented, FTOS sets the size of the fragmented packets to the size specified in this command.
Syntax
ip mtu value
To return to the default IP MTU value, use the no ip mtu command.
Parameters
value Enter the maximum MTU size if the IP packet is fragmented. The
range is from 576 to 9234. The default is 1500 bytes.
Defaults 1500 bytes
Command Modes INTERFACE (Gigabit Ethernet and 10-Gigabit Ethernet interfaces)
Command History
This guide is platform-specific. For command information about other platforms, refer to the
relevant FTOS Command Line Reference Guide .
The following is a list of the FTOS version history for this command.
Version 8.3.19.0 Introduced on the S4820T.
Version 8.3.7.0 Introduced on the S4810.
Version 8.1.1.0 Introduced on the E-Series ExaScale.
pre-Version
6.1.1.0
Introduced on the E-Series.
Usage
Information
When you enter the no mtu command, FTOS reduces the ip mtu value to 1536 bytes. To return
the IP MTU value to the default, use the no ip mtu command.
Compensate for Layer 2 header when configuring link MTU on an Ethernet interface or FTOS
may not fragment packets. If the packet includes a Layer 2 header, the difference between the
link MTU and IP MTU (the ip mtu command) must be enough bytes to include for the Layer 2
header.
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
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