[c-nsp] Jumbo frames on certain VLANs with UCS fabric?

[David Hubbard]

Perfect, thanks Manu.  I switched them all to 9000 but
I would have never found the CoS setting.  I don't
have CoS defined so I read that in that case it defaults
to best effort in the UCS manager so I hand typed 9000
into the drop down and it took it and now I've got
jumbo frame storage traffic to the EMC from vmware at
ten gig.

David 

> -----Original Message-----
> From: Manu Chao [mailto:linux.yahoo at gmail.com] 
> Sent: Tuesday, November 16, 2010 12:53 PM
> To: David Hubbard
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] Jumbo frames on certain VLANs with UCS fabric?
> 
> Hi David,
> 
> (L2) MTU is not per VLAN but per physical interface.
> 
> Make sure all interfaces in a VLAN are configured for jumbo 
> frames before configuring jumbo frame support on an SVI.
> 
> You have to enable jumbo on ALL your 4900 switches interfaces.
> 
> You have to enable jumbo on your UCS (The MTU is set on a per 
> CoS basis in UCS).
> 
> R/
> Manu
> 
> 
> On Tue, Nov 16, 2010 at 5:19 PM, David Hubbard 
> <dhubbard at dino.hostasaurus.com> wrote:
> 
> 
> 	Hi all, I'm working on deploying a UCS system using
> 	iscsi to an EMC with only a pair of 4900M's in
> 	between.  I'm having a bit of trouble wrapping my
> 	head around what I need to do to enable jumbo frames
> 	to make it from end to end on the storage vlan.
> 	
> 	What I've got so far:
> 	
> 	1) Two redundant UCS fabric interconnects are each
> 	in end host mode and each dual-home to the two 4900M's
> 	at ten gig.
> 	
> 	2) Within the UCS configuration, there is a virtual
> 	nic defined as mtu 9000, the rest of the virtual nics
> 	are defined as mtu 1500.
> 	
> 	3) The 4900M's have a storage vlan configured with an
> 	mtu of 9000.  All other vlan's are default 1500.
> 	
> 	4) The ten gig interfaces to the UCS are set as mode
> 	trunk but not mtu 9000 (I think this is an issue?).
> 	
> 	5) The ten gig interfaces to the EMC's two service
> 	processors on each 4900M are configured as
> 	'switchport access vlan...' and 'mtu 9000'.
> 	
> 	6) The two 4900M's have a trunk between them carrying
> 	all vlan's.  (This may be an issue too?)
> 	
> 	
> 	show int on the interfaces to the UCS fabrics and the
> 	switch to switch trunk are both showing mtu 1500.  Do
> 	I need to set all of those interfaces to 9000?  I tried
> 	that, but did not test the EMC connectivity in between
> 	because I noticed as soon as I set that I got a bunch
> 	of MTU_Mismatch showing in "show vlan mtu" and I was
> 	worried I was about to create a big problem.  Or, is
> 	it ok to have the mismatch there because any device
> 	talking on the 1500 byte vlans would not generate a
> 	larger packet anyway but devices on the 9000 byte vlan
> 	are free to talk jumbo and the interfaces will transport
> 	it because it's mtu 9000 all the way through, including
> 	the switch to switch trunk?
> 	
> 	Thanks,
> 	
> 	David
> 	
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