Jumbo MTU UCSM and Nexus 1000v

[Indika Wasala]

Dear all,

What is the correct procedure in setting jumbo mtu in UCSM. As I understand (we don't have any qos policies defined),

1. We need to set mtu 9216 in Best effort QOS policy in LAN Uplinks manager (qos tab).

2. In LAN tab under QOS system class, we need to set 9126 in Best effort QOS policy.

3. We need to set MTU 9126 in each vnic.

In nexus 1000v  we have to define mtu in uplink port profile.

Please correct me if I am wrong.

Thanks...

[Keny Perez]

You are right....

http://jasonnash.com/2011/02/06/enabling-jumbo-frames-on-the-cisco-nexus-1000v/

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus1000/sw/4_2_1_s_v_1_4/interface/configuration/guide/n1000v_if/n1000v_if_4vethernet.html <<<  "MTU cannot be configured on a vEthernet interface."

Don't forget to set Jumbo frames in the rest of the path so that packets dont get dropped and be sure you are aware of your CoS in use so that packets traversing UCS don't go through a CoS that does not have Jumbo frames enabled.

-Kenny

[Indika Wasala]

Thanks Guys..

I think since I don't have any Qos policies, I will have to set the mtu in "best effort" queue in UCS under system Qos classes. Correct ?

[Jarret Gonzales]

Indika Wasala,

Here are some notes I have laying around regarding MTU configurations:

Nexus 1000v vDS

N1kvVSM1#config

N1kvVSM1#port-profile type ethernet {UPLINK - Port profile}

N1kvVSM1#mtu 9000

N1kvVSM1#copy run start
Note: Before 4.2(1)SV1(4) the system mtu command is needed, otherwise it is fixed to 9000

Reference: http://www.cisco.com/en/US/docs/switches/datacenter/nexus1000/sw/4_2_1_s_v_1_5_1/port_profile/configuration/guide/n1000v_port_profile.html

Cisco UCS

     1. In the UCS Manager LAN tab, click LAN Cloud > QoS System Class.

     2. Set the MTU to 9216 on each Priority class as needed. 

     3. You can verify the configuration in the UCS CLI 

UCS # connect nxos

UCS(nxos) # show run | begin system_nq_policy

Look for a policy-map named system_nq_policy.  

Each priority is defined as a class with the type network-qos.  

Each class where mtu was specified in UCSM will reflect the MTU.

GUI Reference: http://www.cisco.com/en/US/docs/unified_computing/ucs/sw/gui/config/guide/2.0/b_UCSM_GUI_Configuration_Guide_2_0_chapter_010011.html#d36386e100a1635

CLI Reference: http://www.cisco.com/en/US/docs/unified_computing/ucs/sw/cli/config/guide/2.0/b_UCSM_CLI_Configuration_Guide_2_0_chapter_010010.html#d23120e98a1635

Hope this helps someone! 

-- Jarret Gonzales