Enabling The Jumbo Mtu - Cisco Nexus 5000 NX-OS Service Configuration Manual

Enabling the Jumbo MTU

Step 3
This example shows how to restore the default queue limit on a Cisco Nexus 2248T Fabric Extender:
switch# configure terminal
switch(config-if)# fex 101
switch(config-fex)# hardware N2248T queue-limit 327680
This example shows how to remove the queue limit that is set by default on a Cisco Nexus 2248T Fabric
Extender:
switch# configure terminal
switch(config)# fex 101
switch(config-fex)# no hardware N2248T queue-limit 327680
Enabling the Jumbo MTU
You can enable the jumbo Maximum Transmission Unit (MTU) for the whole switch by setting the MTU to
its maximum size (9216 bytes) in the policy map for the default Ethernet system class (class-default).
When you configure jumbo MTU on a port-channel subinterface you must first enable MTU 9216 on the base
interface and then configure it again on the subinterface. If you enable the jumbo MTU on the subinterface
before you enable it on the base interface then the following error will be displayed on the console:
switch(config)# int po 502.4
switch(config-subif)# mtu 9216
ERROR: Incompatible MTU values
For Layer 3 routing on Cisco Nexus devices, you need to configure the MTU on the Layer 3 interfaces (SVIs
and physical interfaces with IP addresses) in addition to the global QoS configuration below.
To use FCoE on switch, add class-fcoe in the custom network-qos policy. If already using FCoE, make sure
to add the below lines in the config so that the FCoE does not go down on the switch after enabling the jumbo
qos policy.
switch# conf t
switch(config)# policy-map type network-qos jumbo
switch(config-pmap-nq)# class type network-qos class-fcoe
switch(config-pmap-nq-c)# end
This example shows how to change qos to enable the jumbo MTU:
switch# conf t
switch(config)# policy-map type network-qos jumbo
switch(config-pmap-nq)# class type network-qos class-default
switch(config-pmap-c-nq)# mtu 9216
The system jumbomtu command defines the maximum MTU size for the switch. However, jumbo MTU
Note
is supported only for system classes that have MTU configured.
Cisco Nexus 5000 NX-OS Quality of Service Configuration Guide, Release 5.1(3)N2(1)
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Command or Action
switch(config-fex)# hardware
fex_card_type queue-limit
queue-limit
Purpose
Configures the queue limit for the specified Fabric
Extender. The queue limit is specified in bytes. The range
is from 81920 to 652800 for a Cisco Nexus 2148T Fabric
Extender and from 2560 to 652800 for all other supported
Fabric Extenders.
Configuring QoS on the System
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