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MTU size with Catalyst 3560

I have problem in a wan link, using a wireless equipement. We have 2 catalyst 3560 installed between wireless link. All it?s ok, but when activate a trunk and/or vlan on this wan, I have problem with something exemple, windows autentification?

I found the problem, I must set the mtu at 1496 or lower. But I found nothing in my catalyst for lower mtu under 1500 !

Somebody are idea ?

Thank you.

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Gold

Re: MTU size with Catalyst 3560

Actually, you can change and lower the IP MTU on your routed interface, the ones named vlan1, vlan2 etc.

hope this helps, please rate post if it does!

4 REPLIES
Cisco Employee

Re: MTU size with Catalyst 3560

No you cannot change the MTU size on 3560's to lower than 1500. The default maximum transmission unit (MTU) size for frames received and transmitted on all interfaces on the 3560 switch is 1500 bytes.

You can change the MTU on the switches using " System MTU command" but it cannot be lowered than 1500. You can change it in between 1500-1998.

HTH,

-amit singh

Hall of Fame Super Gold

Re: MTU size with Catalyst 3560

Actually, you can change and lower the IP MTU on your routed interface, the ones named vlan1, vlan2 etc.

hope this helps, please rate post if it does!

New Member

Re: MTU size with Catalyst 3560

Yes I try this, past few days, but the problem are not solved by ajust mtu size in vlan?.

I try to configure sometink like that exemple:

Vlan 100

mtu 1300

This is a good way but, it is not at interface level. I try to apply this value at int vlan 100 but mtu command are not available?.

In test, If I stay configured in trunk and vlan on my wireless link, and I ajust one pc and server at 1300 bytes between wireless link, for exemple, all it?s ok?

I think the solution are to adjust mtu size directly on interface but I learn it is not supported by catalyst lower 1500 bytes. Only supported in router?.

Thank you.

Hall of Fame Super Gold

Re: MTU size with Catalyst 3560

Hi,

conf t

interface vlan10

ip mtu 1490

That's it.

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