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Jumbo ports on a Cisco catalyst 3750

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Last Modified: 2012-06-21
Hi

I have a question to how specific ports can be configured using jumbo frames and leaving other ports with the default mtu 1500.
We have a 4 Switches stacked, 2*ws-c3750g-12s which are our backbone switches and have 48 port 10/100 switches connected to them.
The other 2 switches in the stack are  ws-c3750g-24t and these act server/storage devices connect to them. 4 ports on these switches we want to turn on Jumbo packets for the storage devices.(Netapps fas device) These 4 ports are in 1 vlan and the vlan is only on this stacked switch.  The switches and MTU setting is as below.
switch 1 provision ws-c3750g-12s
switch 2 provision ws-c3750g-12s
switch 3 provision ws-c3750g-24t
switch 4 provision ws-c3750g-24t
system mtu routing 1500
http://www.cisco.com/en/US/products/hw/switches/ps700/products_configuration_example09186a008010edab.shtml 
After looking through the above link I am led to believe that individual ports cannot be configured to accept Jumbo packets, as it is a sytem setting on the switch. Since all the ports in this stacked switch are gig ports this would mean all ports are configured for Jumbo packets ?
So the question is how does one change 4 spercific ports for jumbo packets and leave the other ports to receive packets of 1500.

The ports in question are
Interface portchannel11
Interface portchannel10
interface GigabitEthernet3/0/10
interface GigabitEthernet3/0/11
interface GigabitEthernet4/0/10
interface GigabitEthernet3/0/11

I would be gratefull for any help offered.

bnm-sw012-confg
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Commented:
Yeah I have just been googling and your solution sounds correct, we also just want to segregate the iSCSI traffic we are managing this with a seperste vlan for the iSCSI traffic, and the esx vm servers are in a seperate vlan on the same switch a very similar setup to yourself.

So going from the above, we just have to enable jumbo packets ont the switch.

3750(config)# system mtu jumbo 9000
3750(config)# exit
3750# reload
Then configure the netapps iSCSI trafic to send Jumbo packets.

Thanks

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