From: Dennis J. Hartmann (dennisjhartmann@hotmail.com)
Date: Wed Nov 16 2005 - 10:00:50 GMT-3
The 3550 switch does not support Ethernet Jumbo frames (9000 bytes
to 9K [9,216 bytes] depending on the hardware). This is what puzzled me
even further regarding the VLAN-specific MTU configuration.
-Dennis Hartmann
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Balaji Siva
Sent: Thursday, April 07, 2005 4:17 PM
To: Dillon Yang
Cc: Dennis J. Hartmann; GS
Subject: Re: 3550 MTU Question
The max limit is probably a bug. I don't think any of cat switch hw support
that MTU size. Max is jumbo frame 9k on ethernet switches.
That command max size was probably left over from IOS (token ring days
??)
Even if IOS can send that MTU, it needs to fragmented to send over the
physical link so I think having such MTU size doesn't make any sense.
Fragmentation may be done in software path which doesn't help either.
HTH
Balaji
On Apr 6, 2005 10:42 PM, Dillon Yang <dillony@gmail.com> wrote:
> Hi, Dennis:
>
> The "system mtu" is used for L2 tunnelling, but I have not used "mtu
> 18190" that may be used in fiber environment.
>
> HTH
> dillon
>
>
> On Apr 7, 2005 10:20 AM, Dennis J. Hartmann <dennisjhartmann@hotmail.com>
wrote:
> > Anyone know the difference between the following two commands. I
> > always thought that the 3550 limited Ethernet frames to 1546 bytes
> > and did not allow for Ethernet jumbo frames, but in VLAN
> > configuration I can configure MTU frame sizes up to 18,190 bytes?
Anyone have an explanation on this one?
> >
> > S5(config)#system mtu 1546 ?
> > <cr>
> >
> > S5(config)#vlan 300
> > S5(config-vlan)#mtu ?
> > <576-18190> Value of VLAN Maximum Tranmission Unit
> >
> > Sincerely,
> >
> > Dennis J. Hartmann
> >
> > White Pine Communications
> >
> > dh8@pobox.com
> >
> > CCSI#23402/CCIP/CCNP/CCDP/CCNA/CCDA
> >
> > Cisco IP Voice Support & Design Specialist
> >
> > Cisco Optical, VPN & IDS Specialist
> >
> > MCSE
> >
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