Two ways to enable jumbo frames on Nexus 5K?

[2205_Romy]

Hi,

i have some question about the configuration of the jumbo frames.

Are there two possible configurations to enable the jumbo frames or does I have to enable both?

1.
N5K(config)# policy-map type network-qos jumbo
N5K(config-pmap-nq)# class type network-qos class-default
N5K(config-pmap-c-nq)# mtu 9216
N5K(config-pmap-c-nq)# exit
N5K(config)# system qos
N5K(config-sys-qos)# service-policy type network-qos jumbo

                and

2.
N5K(config)# system jumbo mtu 9216

I could not understand the difference between this two. And, in what direction are they enabled? On all the interfaces in and out?

Can someone explain me, please?

Thanks...

[Atif Awan]

2205_Romy wrote:
Hi,
i have some question about the configuration of the jumbo frames.
Are there two possible configurations to enable the jumbo frames or does I have to enable both?
1. 
N5K(config)# policy-map type network-qos jumbo
N5K(config-pmap-nq)# class type network-qos class-default
N5K(config-pmap-c-nq)# mtu 9216
N5K(config-pmap-c-nq)# exit
N5K(config)# system qos
N5K(config-sys-qos)# service-policy type network-qos jumbo
                and
2.
N5K(config)# system jumbo mtu 9216 
 
I could not understand the difference between this two. And, in what direction are they enabled? On all the interfaces in and out?
Can someone explain me, please?

Thanks...

Jumbo MTU is configured using the first option you mentioned. The second command just sets an upper limit for the jumbo MTU which is 9216 by default. If you just want to enable 9216 byte jumbo frame support then use the command set in your option 1.

Atif

[2205_Romy]

Thanks for answer.

Then I need to configure the first option for incoming jumbo frames from the server.

But, if the server sends this jumbo frames to the Nexus, does the Nexus fragment this frame,

before it sends it to the backbone Cat6500?

Thanks.

[Atif Awan · Accepted solution]

2205_Romy wrote:
Thanks for answer.
Then I need to configure the first option for incoming jumbo frames from the server.
But, if the server sends this jumbo frames to the Nexus, does the Nexus fragment this frame,
before it sends it to the backbone Cat6500?
Thanks.

No. Fragmentation is done at L3 boundaries while N5K is an L2 switch (am talking about the previous revision of the switch : 50x0).

Atif

[2205_Romy]

Ok. I have a Nexus 5020 L2.

Does the port (channel) on the 6500 (mtu 1500) see the jumbo frames as giants and drop them?

Can I shut down the jumbo frames on the ports to the Cat6500? Or have you another idea?

Thanks.

[Atif Awan]

2205_Romy wrote:
Ok. I have a Nexus 5020 L2. 
Does the port (channel) on the 6500 (mtu 1500) see the jumbo frames as giants and drop them?
Can I shut down the jumbo frames on the ports to the Cat6500? Or have you another idea?
Thanks.

What exactly are you trying to achieve here?

Atif

[2205_Romy]

I would like send jumbo frames from server over the nexus to the 6500, but the 6500 doesnt support jumbo frames.

Can I do so with a seperat policy map for the interface to the backbone, who sets the mtu to 1500?

And when I do so, does I have two policy maps (+ default) on this interface?

[Atif Awan]

2205_Romy wrote:
I would like send jumbo frames from server over the nexus to the 6500, but the 6500 doesnt support jumbo frames.
Can I do so with a seperat policy map for the interface to the backbone, who sets the mtu to 1500?
And when I do so, does I have two policy maps (+ default) on this interface?

Which line card do you have on the 6500? If 6500 does not support jumbo frames (assuming you have an older line card) then what is the point of enabling them? The only advantage I can see in enabling jumbo frames is for server to server communication involving only N5K.

Atif

[2205_Romy]

The line card doesnt support jumbo frames.

I have now enabled the jumbo frames for all interfaces for Server to Server communication.

But I would like to know that no jumbo frames go out of the interface wich is bounded to the Cat6.

Can change the mtu here on this interfaces to backbone back to mtu 1500 max?

Thanks

[2205_Romy]

Oh... I think I understand know.

You are rigth, no fragmentation on this L2 Nexus. I can not disable jumbo mtu on the interface to the backbone, bacause I have enabled it global on the system and consistently to ech interface.

First I will take it off and then I look forward to the Nexus 7000 in the next year.

Many thanks to you.

Best regards

[Atif Awan · Accepted solution]

2205_Romy wrote:
Oh... I think I understand know.
You are rigth, no fragmentation on this L2 Nexus. I can not disable jumbo mtu on the interface to the backbone, bacause I have enabled it global on the system and consistently to ech interface.
First I will take it off and then I look forward to the Nexus 7000 in the next year.
Many thanks to you.
Best regards

Good to know there is no additional confusion. By the way you can leave the configuration ON if that will facilitate your server to server communication. Server to outside communication should still negotiate the proper TCP MSS automatically so the lack of jumbo frame support on the 6500 should not be a major concern.

Atif

[2205_Romy]

Thanks for additional information.  Than I will do so.

Have a great weekend!

[aain]

Hi Romy what's the command for applying the policy map  to the interface ?

[amarhingmire]

Policy creation with Jumbo capabilities

N5K(config)# policy-map type network-qos jumbo
N5K(config-pmap-nq)# class type network-qos class-default
N5K(config-pmap-c-nq)# mtu 9216
N5K(config-pmap-c-nq)# exit

Apply policy globally for all the interfaces.

N5K(config)# system qos
N5K(config-sys-qos)# service-policy type network-qos jumbo

Hope this is clear on how to.