Jumbo frame for iSCSI on Nexus 5624Q

[Jeremy Dubrulle]

Hi everyone, I know there are some topics about Jumbo but not with iSCSI.

My goal is to enable jumbo frame support on my Nexus 5624Q (I will receive them soon) only for iSCSI traffic.

I'm not sure about the config (especially because I don't have the switches yet to test) but here is what I think I should do :

N5624Q(config)# class-map type qos match-all iSCSI

N5624Q(config-cmap-qos)# match protocol iscsi

N2564Q(config)# policy-map type qos Policy-QoS

N2564Q(config-pmap-qos)# class iSCSI

N2564Q(config-pmap-c-qos)# set qos-group 2

N2564Q(config)# class-map type network-qos iSCSI

N2564Q(config-cmap-nq)# match qos-group 2

N2564Q(config)# policy-map type network-qos Jumbo

N2564Q(config-pmap-nq)# class type network-qos iSCSI

N2564Q(config-pmap-c-nq)# mtu 9216

N2564Q(config-pmap-c-nq)# pause no-drop

N2564Q(config-pmap-c-nq)# exit

N2564Q(config-pmap-nq)# class type network-qos class-default

N2564Q(config)# system qos

N2564Q(config-sys-qos)# service-policy type network-qos Jumbo

N2564Q(config-sys-qos)# service-policy type qos input Policy-QoS

Is it good to get the Jumbo ok for the iSCSI traffic and do nothing for the rest of the traffic? Do I need another command to permit jumbo on interfaces?

[Andrea Testino · Accepted solution]

Hi Jeremy,

Typically what we see is that most customers configure jumbo frames for both iSCSI traffic as well as the rest of the traffic as you could see some odd interop issues otherwise - There's no harm in doing this.

Here's a sample config from a Nexus 5K with jumbo for both:

policy-map type network-qos jumbo-qos
	class type network qos class-fcoe
		pause no-drop
		mtu 2158
	class type network-qos class-default
		mtu 9216
		multicast-optimize
!
system qos
	service-policy type network-qos jumbo-qos

Additionally, you will probably want to configure jumbo frames to whatever the upstream device for the Nexus 5Ks is. For example, a Nexus 7000 pair.

Hope that helps.

- Andrea

[Jeremy Dubrulle]

Hi Andrea, thanks I thought it was better to permit the Jumbo for the traffic that needs it, and that it could affect performance.

But if you tell me that it's a best practice to permit Jumbo globally so that's fine.