Newb Question on Jumbo Frames

[bigpomaha]

We have a Metro connection setup for replication and we are getting a lot of re-transmits with our storage and they (Dell) made a few suggestions.  Currently our SYSTEM MTU is set to 9000 but they suggest 9198.  First, does that make sense and second is there any interruption on our production side  if we change the MTU size??  Also they want us to change the command from system mtu routing 9000 to system mtu jumbo 9198.  

Just need a little clarification if possible.  Also we are running a catalyst 3750.  Any comments or suggestions are welcome.  Thanks in advance!

Perry

[SANTHOSHKUMAR SARAVANAN]

Hi ,

 If your switch model is 3750 it wont support jumbo frame 9198 

http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6000-series-switches/24048-148.html#c9

HTH

Sandy

[bigpomaha]

Thanks for the heads up.  after looking at things i realized that we have  a 3750 - X and I think that one will let you go up to 9198.  Is that correct?? 

[SANTHOSHKUMAR SARAVANAN · Accepted solution]

Yes it supports

Standalone Catalyst 3750-X, 3750-E, 3560-X or 3560-E switch or Catalyst 3750-X-only or Catalyst 3750-E-only stack	You can enter the command on on a Catalyst 3750-X, Catalyst 3750-E, Catalyst 3560-X, or Catalyst 3560-E switch, but system MTU value does not take effect. 1	Use thesystem mtu jumbo bytescommand. The range is from 1500 to 9198 bytes.	Use the system mtu routing bytescommand. The range is from 1500 to the system jumbo MTU value (in bytes).2
Mixed hardware stack	Use the system mtu bytes command, which takes effect only on Catalyst 3750 members.1 The range is from 1500 to 1998 bytes.	Use thesystem mtu jumbo bytescommand. The range is from 1500 to 9000 bytes.	Use the system mtu routing bytescommand. The range is from 1500 to the system MTU value (in bytes).2
Catalyst 3750-only stack Catalyst 3750 switch Catalyst 3560 switch	Use the system mtu bytes command. The range is from 1500 to 1998 bytes.	Use thesystem mtu jumbo bytescommand. The range is from 1500 to 9000 bytes.	Use the system mtu routing bytescommand. The range is from 1500 to the system MTU value (in bytes).

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12-2_53_se/command/reference/3750xcr/cli3.html#wpmkr3079919

Usage Guidelines

The switch does not support the MTU on a per-interface basis.

The system mtu bytes global configuration command only affects the system MTU size on Fast Ethernet ports on Catalyst 3750 members in a mixed hardware switch stack. In this stack, you can use the system mtu bytes global configuration command on a Catalyst 3750-E or Catalyst 3750-X member to configure the system MTU size on a Catalyst 3750 member. If you enter the system mtu bytes global configuration command on a Catalyst 3750-E or a 3560-E switch, the command does not take effect.

The system mtu, system mtu jumbo, and system mtu routing global configuration commands do not take effect in these cases:

•When you enter the system mtu command on a Catalyst 3750-E or 3560-E switch

•In a mixed stack when you enter the system mtu jumbo command for the Fast Ethernet ports on a Catalyst 3750 member

•When you enter the system mtu routing command on a switch on which only Layer 2 ports are configured

---

Note This command is not supported on switches running the LAN base feature set.

HTH

Sandy