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We want to enable 9K jumbo frame on CISCO WS-C2960X-24PS-L switches, however I found this line in the documentation and it made me confused and concerned because it involves reset and reload of switch aside from setting it globally.

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

Is there any possibility of setting it for some interface without having to restart the switches or affecting MTU of other ports? Can't afford downtime unless absolutely necessary. We were looking into this as an improvement for Oracle RAC private interconnect ports' communication. We have bunch of other servers on these switches we don't want to touch.

Rest of the paragraph:

When you use this command to change the system MTU or jumbo MTU size, you must reset the switch before the new configuration takes effect. The system MTU setting is saved in the switch environmental variable in NVRAM and becomes effective when the switch reloads. The MTU settings you enter with the system mtu and system mtu jumbo commands are not saved in the switch IOS configuration file, even if you enter the copy running-config startup-config privileged EXEC command. Therefore, if you use TFTP to configure a new switch by using a backup configuration file and want the system MTU to be other than the default, you must explicitly configure the system mtu and system mtu jumbo settings on the new switch and then reload the switch. Gigabit Ethernet ports operating at 1000 Mb/s are not affected by the system mtucommand, and 10/100-Mb/s ports are not affected by thesystem mtu jumbo command.
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2 Answers 2

Reset to default
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No, it is not possible to change the MTU for a single interface, nor is it possible to change the MTU without a reload on your switch platform.

The documentation you provided explicitly confirms this statement and describes why.

Environmental variables such as MTU or configuration registers are global variables. This means it affects the entire switch. The switch loads its environmental variables during the switch boot process, prior to the loading of the switch configuration.

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  • Well that settles it. I'm wondering if only L3 and above Cisco switches support this. Commented Jul 10, 2017 at 14:23
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Sorry to be the bearer of bad news, but as far as I am aware, setting individual MTU per port isn't supported on the 2960 platform. Your only choice here is a reboot of the switch setting the MTU globally.

Other platforms do support this behavior, but not the 2960 series.

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  • Someone tested in his lab for me, indeed it is not supported. Commented Jul 10, 2017 at 14:22