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Beginner

3750 MTU size definition

Max MTU size for 3750 (quite old box, but still fine) is 9000.

Is it 'brt' value with tag (14) or 'net' without it?

Let me know :)

 

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Hall of Fame Master

Re: 3750 MTU size definition

Hello mig1anc,

being the Cisco 3750 an IOS based switch the MTU refers to the L3 payload size

so the actual max L2 frame size should be 9000 + 14 bytes + 4 bytes FCS = 9018 bytes

for 802.1Q tagged frames there is an additional overhead of 4 bytes at Level 2.

To be conservative you should consider to be able to carry IPv4 or IPv6 packets of size 8996 bytes in 802.1Q tagged frames.

To be noted in other Cisco NOS like IOS XR the MTU refers to the L2 MTU and includes 14 bytes of L2 overhead (the final 4 bytes of FCS are not included).

 

Hope to help

Giuseppe

 

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Beginner

Re: 3750 MTU size definition

That's exactly what I was looking for, thanks
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