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New Member

Mismatched MTU on Trunk Link

Hey folks!

I'm a bit confused and need some guidance.  We have a 4510 connected to a Nexus 3064.  Our SAN, server management NICs and server iSCSI NICs will be connecting to the Nexus.  We wanted to use, or at least test, jumbo frames.  Based on the research I've done, it seems like the Nexus 3064 is all or nothing when it comes to MTU - instead of doing per interface or per VLAN.  

With that being said, my trunk port between the Nexus and 4510 is going to be mismatched... one end will have 1500 and the other will have 9000.  All the jumbo frames will be isolated to the Nexus and won't traverse the trunk link.  Is this OK?  Will it cause any problems?  Is there a better way to do this?

 

Thanks... please let me know if you need more info!

mitch

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Super Bronze

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The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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Posting

Mitch, NICs on the same wire can be configured to have different MTUs.  The issue to watch for is one NIC sending a frame larger than the other NIC can receive.  Unlike L3, L2's sender won't fragment, it will send the too big frames, and the receiver will drop them.

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VIP Super Bronze

Hi Mitch,It should work fine.

Hi Mitch,

It should work fine.  The 5500 series are also the same.  When you enable system qos policy with jumbo frame, it applies to the entire switch.

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus3000/sw/qos/503_u3_1/b_Cisco_Nexus_3000_QoS_Config_Guide_Release_503_U3_1/b_Cisco_Nexus_3000_QoS_Config_Guide_Release_503_U3_1_chapter_011.html

 

HTH

New Member

Thanks Reza. Any other

Thanks Reza.

 

Any other thoughts or opinions?  Just generally speaking, is it OK for one end of a trunk to have a different MTU than the other end?

Super Bronze

DisclaimerThe Author of this

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Mitch, NICs on the same wire can be configured to have different MTUs.  The issue to watch for is one NIC sending a frame larger than the other NIC can receive.  Unlike L3, L2's sender won't fragment, it will send the too big frames, and the receiver will drop them.

New Member

Thanks Joe.  I was hoping you

Thanks Joe.  I was hoping you might chime in - your posts are always helpful.

 

Thanks to you too, Reza.

 

 

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