Wireless Access

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Contributor II
Posts: 70
Registered: ‎05-01-2015

MTU issure

Hi guys,

 

How does the layer 2 switch process the packet when the packet is bigger than the MTU of the switch's interface?

There are 2 situations:

1, How does the layer 2 switch process the ingress packet.

2, How does the layer 2 switch process the egress packet.

 

For the first question, I'm sure we all know the answer. And it proves that the layer 2 switch would check the FCS field of the frames, because the layer 2 switch would drop the frame whose size is bigger the MTU of the interface.

 

But how would the switch act if the interface's MTU are different?

MTU.jpg

 

I asked another question about this, and thanks to Armand Wang,what  I really should ask.

Like the Pic above, How does the switch's port 2 process the packet port 1 received a frame whose size is bigger  than the Port 2's MTU?

MVP
Posts: 562
Registered: ‎11-28-2011

Re: MTU issure

In my experience, it would depend on the switch, and the way the software on it is written.

 

Most I've worked with check MTU on ingress, and not egress.

 

Kudos appreciated, but I'm not hunting! (ACMX 104)
Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: MTU issure

I did the experiment today, and the result just liked the Pic shown.

 

So it should be like the way you said. Only check the ingress, and don't check the egress. 

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