Jumbo MTU Cheatsheet

How the maximum MTU is configured across the different CCIE DC lab devices is fairly complex and varied.  I've condensed my understanding of how to configure in the document below.  For reference material I used the fantastic post by Peter Revill (http://www.ccierants.com/2013/10/ccie-dc-definitive-jumbo-frames.html) and various Cisco documents.  Any mistakes are clearly mine.

N7K
  1. System jumbomtu sets the MTU across the system to for L2 interfaces only to 9216
  2. If using M interface, must set MTU under the interface
  3. If using F interface, the MTU is set similar to a 5K

N5K
system MTU
1.  Do a show policy-map type network
2.  Copy the output into notepad
3.  Change the ‘class type network-qos class-default’ MTU to 9216
4.  Change the name of the policy-map to something like JUMBO
5.  Paste the policy-map back into the 5K
6.  Activate the new service-policy
 system qos
 service-policy type network JUMBO
L3 Int MTU
1.  The MTU must be set on the L3 interface.  It will only show a 1500 MTU - cosmetic only

N1Kv
1. The system jumbomtu command does nothing
2. MTU only needs to be configured on the uplinks.  The vEthernet interfaces support jumbo by default.

General Nexus
SVI - always set MTU
Port-channels - 7K must config, 5K comes from System Class
VPC - Peer-Link already 9216 and can’t change. On 7K PC needs to be set with MTU command
FabricPath - 7K and 5K have same rules as usual. 7K change system MTU or MTU under interface. On 5K change the System Class
OTV - Join interface and Extended VLANs need MTU set
FC - per VSAN

UCS
1.  Since the FI is based from the 5K, the ‘QoS system class’ is where the MTU is set within UCS
2.  There is an MTU setting under the vNIC - this is used to inform the OS that the network cards supports whatever value is entered here.

MDS
1. The MDS mtu is set under the Gigabit interface with a ’switchport mtu xxxx’.  Cisco recommends 3000 and the max is 9000.