Jumbo frame Config

[Patrick McHenry]

Hi

I'm looking to enable jumbo frame support on a 3750X for some 3PAR iSCSI storage. All switches in the stack are IPBASE.

From what I have read, after entering "system mtu jumbo 9000" I have to reload the switch.

I have four questions:

1. Must I configure "system mtu jumbo 9000" on all switches in the stack or do I only configure it on the master switch?

2. If Jumbo frame traffic will be traversing VLANs/subnets will I also have to configure "system mtu routing 9000"

3. If jumbo frames traffic will be traversing VLANs/subnets will I also have to enable jumbo frame on the SVI? (the reason I ask is because I have seen some documentation that says I must enable jumbo on the SVI, but I don't see the jumbo syntax in the CLI.

CORE-SW(config-if)#ip mtu ?
  <68-1500>  MTU (bytes)

4. Is this because I haven't enabled jumbo on the switch yet?

Thank you

PS:

I just did a "show system mtu" and got this output:

System MTU size is 1500 bytes
System Jumbo MTU size is 9000 bytes
System Alternate MTU size is 1500 bytes
Routing MTU size is 1500 bytes

So it appears the mtu has been set to 9000...funny I don't see it in the config though. Looks like I will have to enable "system mtu routing" though...

[Reza Sharifi]

Hi Patrick,

1-Master only.  The config will sync to other switches.

2-Yes

3-No, on the small switches (3650, 3750, 3850, etc..) Jumbo frame can only be enabled globally.

4-No, on theses switches adding it to SVI is not supported (only globally).

HTH

[Patrick McHenry]

Thanks Reza,

I just did a "show system mtu" and got this output:

System MTU size is 1500 bytes
System Jumbo MTU size is 9000 bytes
System Alternate MTU size is 1500 bytes
Routing MTU size is 1500 bytes

So it appears the mtu has been set to 9000...funny I don't see it in the config though. Looks like I will have to enable "system mtu routing" though...

I believe enabling the mtu routing config does not require a reload?

Thanks

[Reza Sharifi]

Patrick,

I believe enabling the mtu routing config does not require a reload?

I don't remember if it requires it or not, but since you need jumbo for iSCSI traffic, I don't think you need to enable mtu for routing.

HTH

[Patrick McHenry]

Thanks Reza - I guess I will find out from the vendor