Enabling Jumbo frames

[stefano.tellini]

Hi all,
I need some support to enable jumbo frames on a LAN composed by some Cisco 3750, 3750-E, 3560-E and 4900M.
The 3560-E acts as the Core switch and it is connected via 10 Gbps trunk links to the LAN as per scheme attached.

The customer needing is to enable jumbo frames only on some links/vlans: for example Vlans 27 and 1 are not intrested in Jumbo frames capability.
In particular he is interested in enabling jumbo frames on Vlan 21 in order to use this capability with the highlighted New Storage Server.

Is it possible to enable jumbo frames only on some ports on 3750-E, 3560-E, 3750 and 4900 model switches or is it necessary to enable it as a global configuration?
Is it a capability referred to IOS version or is it a hardware limit/setting?
The list of IOS actually working is the following:

3560-E -> 12.2(46)SE
3750-E -> 12.2(46)SE
4900 ->12.2(46)SG
3750 -> 12.2(25)SEA

Another question: is it necessary to enable jumbo frames on each end of a link?
What if one end has jumbo frames enabled and the other one not?
Does the switch with disabled jumbo frames continue flooding L2 frames (for example splitting bigger frames) or does it drop the bigger ones?
Looking at some similar post it seems to me that jumbo frames are discarded if they arrive on layer 2 interfaces with disabled jumbo frames, while they are forwarded if they go through layer 3 interfaces.

Did anybody pass through similar issues?

Many thanks in advance for your suggestion.
Stefano

[Shelley Bhalla]

Hope these will help:

Catalyst 3750/3560 Series

Catalyst 3750/3560 Series switches support an MTU of 1998 bytes for all       10/100 interfaces. All Gigabit Ethernet interfaces support jumbo frames up to       9000 bytes. The default MTU and jumbo frame size is 1500 bytes. You cannot       change the MTU on an individual interface. You must set the MTU globally. Reset       the switch afterwards for the MTU change to take effect.

If Gigabit Ethernet interfaces are configured to accept frames           greater than the 10/100 interfaces, jumbo frames that ingress on a Gigabit           Ethernet interface and egress on a 10/100 interface are dropped.

http://www.cisco.com/en/US/products/hw/switches/ps700/products_configuration_example09186a008010edab.shtml

Shelley.

[stefano.tellini]

Thanks Shelley!

Does the E series has the same behaviour or does it have better capabilities? And any hints about 4900-M?

[Shelley Bhalla]

Jumbo frame support does not change regardess of E Series or not.

for 4900, Yes Jumbo frame suport is there:

http://www.cisco.com/en/US/partner/prod/collateral/switches/ps5718/ps6021/product_data_sheet0900aecd8017a72e.html

and the same limitations apply to them as well.

Regards

Shelley.

Please rate if this helped.

[stefano.tellini]

Hi all,
I need some other hints.
We suppose we can go with Jumbo frames on all the devices illustrated in the Visio scheme on the first post. Anyway we need to continue to interact this LAN to the "Main LAN" cloud.
We are going to install as edge devices of this cloud a new couple of switches 6504-E model; the trunk link to the 3560-E will be provided via a couple of 10 Giga port from a WS-X6704-10GE blade (redundant structure).

Will it be possible to activate Jumbo frames on port basis on the trunk link of the 10Giga blade of new 6504 without interfering with standard settings for the other "cloud devices" (they won't support Jumbo frames as they are 100Mb port switches)?

Can the 6504-E manage the different lenght frames on different ports without discarding any of them?

Thank you again for your suggestions.
Best regards,
Stefano