Enabling jumbo frame in a legacy environment

[jhontoc24]

Hi Team

in a few days I will renovate 2 legacy 6500 in VSS mode with a pair of c9500.

They will be a collapse core in a very legacy envirotment and our customer asks me to enable jumbo frame in these cores. I'm afraid if I enable globally system mtu 9000, it could impact downlinks connections with legacy accesss switches, routers or firewall connect directly with this core.

is it a recomendation to go for it? or should i tell to my customer keep with the default MTU.

thanks,

Jhon

[balaji.bandi]

Instead of Global Level, why not enable on inerface level, so it will not effect as per your concern.

make sure you have right  module support for jumbo frames, some modules do not support

here is support and not supported one.

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/12-2SX/configuration/guide/book/intrface.html

[Reza Sharifi · Accepted solution]

Hi BB,

The 9500 support enabling Jumbo frame globally only.

see link:

When configuring the system MTU values, follow these guidelines:

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

• If you enter the system mtu bytes global configuration command, the command affects all the ports on the switch.https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9500/software/release/16-8/configuration_guide/int_and_hw/b_168_int_and_hw_9500_cg/b_168_int_and_hw_9500_cg_chapter_011.html

• To the OP (Jhon),
• Enabling Jumbo frame on the 9ks should not effect the connectivity to other legacy switches that are configured with default MTU size(1500). Firewalls may not like it. That said, since there is no benefit in enabling it only on one platform and not other switches, I recommend keeping everything at default
• HTH

[balaji.bandi]

@Reza Sharifi  - Thank you and i am ware of that. in related to Cat 9500..may be i miss read the comms here.

orginal poster requeted to enable on 6500 with 9500, So i was in impression, Cat 9500 going to be new model (so i belive this not production one, this is only my assumption)

So i have provided thinking that he could enable Cat 6500 per interface level.

T