Jumbo frames nexus 9300 to Cat3850

[MrNo]

Hi, I want to enable jumbo frames bettwen nexus 9300 and cat3850.

nexus is on NXOS: version 9.3(8)

cat is on IOS XE Software, Version 16.09.05

On nexus side I have set 

sh int po1

interface port-channel1
description MTU9k
switchport access vlan 555

mtu 9216
vpc 26

member of portchannel is eth24

interface Ethernet1/26
description MTU9k
switchport access vlan 555
mtu 9216
channel-group 26 mode active

Cat3850 conf is:

Global Ethernet MTU is 9000 bytes.

interface Port-channel2
description MTU9k
switchport access vlan 555
switchport mode access

Members in this channel: Gi1/0/20 Gi2/0/20

interface GigabitEthernet1/0/20
description MTU9k
switchport access vlan 555
switchport mode access
channel-group 2 mode active

interface GigabitEthernet2/0/20
description MTU9k
switchport access vlan 555
switchport mode access
channel-group 2 mode active

when I try to ping from cat to nexus it works. But if I set size to anything above 

[MrNo]

when I try to ping from cat to nexus it works. But if I set size to anything above 1500 it fails. What am I missing?

[MHM Cisco World]

• System MTU--This value applies to switched packets on the Gigabit Ethernet and 10-Gigabit Ethernet ports of the switch. Use the system mtu bytes global configuration command to specify the system jumbo MTU value.
• Protocol-specific MTU--This value applies only to routed packets on all routed ports of the switch or switch stack. Use the ip mtu bytes or ipv6 mtu bytes interface configuration command to specify the protocol-specific MTU value.
  
  use system MTU in 3850 because the packet is switch.

[MrNo]

Hi, thanks for replay.

cat3850 conf is:

Global Ethernet MTU is 9000 bytes.

Is this OK? 

Also: 

I am not shure about this one

sh vlan mtu

VLAN SVI_MTU MinMTU(port) MaxMTU(port) MTU_Mismatch
---- ------------- ---------------- --------------- ------------
555- 9000 9000 No

Is ti OK to have value 9000 on SVI_MTU on vlan555?

[MHM Cisco World]

sorry you already config MTU in global mode of 3850. so that OK 
for NSK 

Per-Port MTU Configuration

Nexus 3000: Includes Nexus 3132Q-V, 3164, 31108, 31128PQ, 3200 Series, and 36180YC-R switches

Neuxs 7000: All Nexus 7000- and 7700 Series switches

Nexus 9000: All Nexus 9200 Series switches (includes 92xxx), 9300 Series switches (includes 93xxx), and 9500 Series switches

For platforms that use Per-Port MTU Configuration L2 ports can use only the System Jumbo MTU configured on the switch or 1500. By default System Jumbo MTU is 9216.

L2 ports configured with Jumbo MTU automatically updates to the new value if it is changed.

Nexus# show running-config all | i jumbomtu
system jumbomtu 9216

Nexus(config)# system jumbomtu ?
<1500-9216> Enter jumbomtu

Configure and Verify Maximum Transmission Unit on Nexus Platforms - Cisco

[MrNo]

Hi is it really nessesary to enable system mtu to 9000? I am really not comfortable with that. I am not shure waht will happend. I have mtu 9216 enabled on portchannel and phy int. Also, there are two hosts on nexus and Jumbos are flying wheel bettween them. Only problem is that Jumbos are not working bettwen switches.

[Reza Sharifi]

If this is just for layer-2 traffic between the switches, you don't need to enable system mtu on the nexus. All you need is "mtu 9216" under the physical interface or Portchannels. To verify the mtu is applied correctly, use "sh int ex/x | in MTU"

HTH

[MHM Cisco World]

I will share note with you, today or tomorrow.

[MHM Cisco World]

I dont why the Cisco make it more complex 
first the platform divide into two 
platform that not support MTU under interface 
platform that support MTU under interface, here the MTU you config under the interface (per-port) must be within range the jumbo frame size you config in system.  
to be sure I run lab and check this point. 
thanks 
MHM 

[MrNo]

First, I am sorry.

System mtu 9000/9216 is enabled on both switches.

Only nexus have mtu set to 9216 on port.

All hosts are in same vlan.

jumbo works between hosts on nexus and also between hosts on 3850, but jumbo is still not working between switches.

Is there any diagnostic tool or log so I can figure out what I am doing wrong?

[MHM Cisco World]

when I try to ping from cat to nexus it works. But if I set size to anything above 
can you try ping from Host not from NSK or SW, 
the MTU jumbo size have two level 
for L2 you can config under L2 port 
and L3 you must config it under SVI 
but to be sure ping from Host in Cat to Host in NSK with large MTU size.