Re: MTU

Ok, thanks for the responses but i am still confused.

Would i be right in saying that the MTU on a switch cannot be changed
at an interface level.
Therefore if we want to change the MTU we would either need to use the
"system mtu" command or change the MTU
on a specific VLAN. So what is the difference between these two methods?

Thanks

On Tue, Aug 31, 2010 at 7:13 PM, Marcelo Rosa <MRosa_at_multirede.com.br> wrote:
> My understanding:
>
> L2 reports, say, 1500B MTU do L3 (you configure it with mtu)
> L3 knows its header is 20B long,so it reports 1480B to L4 (you configure it with ip mtu)
>
> MR
>
> -----Mensagem original-----
> De: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] Em nome de Sonu Khandelwal (sokhande)
> Enviada em: terga-feira, 31 de agosto de 2010 14:48
> Para: GAURAV MADAN; Yaseen Mirza
> Cc: Cisco certification
> Assunto: RE: MTU
>
> Hi Gaurav,
> As per my understanding Ip mtu will include l3 header (20 byte ip
> header) but not l2 header.
>
> Others correct me if I am wrong.
>
> Thanks,
> Sonu
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> GAURAV MADAN
> Sent: Tuesday, August 31, 2010 10:54 PM
> To: Yaseen Mirza
> Cc: Cisco certification
> Subject: Re: MTU
>
> Well ... I was reading some archives some time back and found that
> interface level "mtu " command is the max length of unit that can be
> processed and this includes L2 + L3 header length as well
>
> CLI "ip mtu" is size of payload that can be sent and don't include L2
> + L3 header length
>
> Someone please correct me if I am wrong .
>
> Thnx
> Gaurav Madan
> CCIE # 23863
>
> On Tue, Aug 31, 2010 at 8:42 PM, Yaseen Mirza <yaseengs_at_gmail.com>
> wrote:
>> Hi
>>
>> Can someone explain the difference between the following MTUs
>>
>> From what I can understand there is a hardware MTU.
>>
>> interface f1/0
>> mtu 1500
>>
>> Then there is an IP MTU for only IP packets
>>
>> interface f1/0
>> ip mtu 1500
>>
>> The most confusing is vlan MTUs
>>
>> Under what circumstance does the VLAN MTU come into play For instance
>> if I change the MTU under a layer2 vlan what effect does it have and
>> how is this different from changing the MTU under an SVI?
>>
>> Thanks
>>
>>
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Received on Tue Aug 31 2010 - 23:44:35 ART