In a typical 3 tiered infrastructure I would assume it must be commonplace 
practice to house some vlans with Jumbo frames support.  We have 2 options 
currently connecting devices from access to distribution.

Access          Distribution
3550    <->     6500
4500    <->     6500

We have customers segmented on L2/L3 vlans requesting Jumbo frames in various 
environments.  Some request separate hardware altogether like for Oracle RAC.  
How have you guys seen this implemented?

Cheers,

// LeBlanc


On Dec 28, 2009, at 1:40 PM, Mack McBride wrote:

> If jumbo frames are enabled on edge ports but not in the middle there can be 
> issues.
> Layer 2 will not fragment packets and layer 3 will fragment in software.
> It is better to have jumbos in the middle but not on the edges where there 
> will not be issues.  Basically the smallest packet size should be at the edge 
> and the core
> should have a larger size than the edge.
> 
> LR Mack McBride
> Network Architect
> Viawest, Inc.
> 
> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]] On Behalf Of Jason LeBlanc
> Sent: Monday, December 28, 2009 10:09 AM
> To: Marko Milivojevic
> Cc: [email protected]
> Subject: Re: [c-nsp] MTU Mismatch
> 
>> From a routing perspective this makes sense.  Will there be any adverse 
>> effects if the Jumbo frames is bumped up anywhere in the chain?  Meaning L2 
>> vs. the L3 Routing.  I believe thats where the MTU path discovery comes into 
>> play correct?  Sorry to add to this but while we were on the subject I 
>> figured I would ask :)  We want to use jumbo frames in a few environments 
>> but not at the cost of anything in the path.
> 
> Cheers,
> 
> // LeBlanc
> 
> On Dec 28, 2009, at 9:09 AM, Marko Milivojevic wrote:
> 
>> On Mon, Dec 28, 2009 at 16:00, Mohammad Khalil <[email protected]> wrote:
>>> 
>>> i have checked the mtu on 3750
>>> sh system mtu
>>> 
>>> System MTU size is 1500 bytes
>>> System Jumbo MTU size is 1512 bytes
>>> Routing MTU size is 1500 bytes
>>> 
>>> but there is no such command on the 6523
>> 
>> Different beast, but at least you get the explanation. As far as
>> routing processes go, MTU on 3750 is 1500. On 6500 you can set it per
>> interface (depending on the LC).
>> 
>> --
>> Marko Milivojevic - CCIE #18427
>> Senior Technical Instructor - IPexpert
>> 
>> Mailto: [email protected]
>> Telephone: +1.810.326.1444
>> Live Assistance, Please visit: http://www.ipexpert.com/chat
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