Minimum Packet Size

[sivam siva]

Hi

Have a basic Doubt

what is the minimum packet size to transmit ?

I have studied that its 64 bytes , 

but some websites says 68 , is it true ?

also i found the packet size below that value , which is  44 bytes for the EIGRP packet (I did this test in serial interface) , is there any exception for control traffic ?   

please Find the attached photo which shows packet with 44 bytes

Thanks in advance.

[balaji.bandi]

i would suggest have look,there was  already have massive dicussion here to understand :

https://community.cisco.com/t5/switching/slot-time-and-minimum-ethenet-fame-size/td-p/2797341

still have any more questions, please ask.

[Joseph W. Doherty]

"also i found the packet size below that value , which is 44 bytes for the EIGRP packet (I did this test in serial interface) , is there any exception for control traffic ? "

Different media have different minimums. I.e. your serial medium likely supports a smaller packet size.

BTW, hope it's clear in the reference that Balaji provided, but much of Ethernet's minimum packet size requirement is due to half duplex media requirements - an example of a common issue where newer technology is often limited by keeping compatibility with earlier standards.

[sivam siva]

@Joseph W. Doherty  @balaji.bandi 

As peter told frame size must be at least 64 bytes ( which is slot-time of Ethernet to detect the collision ),

so even if the data is not sufficient, device must pad 0s to come up with 64 byte frame. this i could understand.

But if you see my below output Ethernet interface transmits EIGRP packet with 60 bytes , how its possible ?

 

[Joseph W. Doherty]

It might not be counting the FCS (4 bytes).

[sivam siva]

@Joseph W. Doherty 

I think you are right, could you tell me is there any way to confirm it ?

so that I can conclude.

[Joseph W. Doherty]

Expand the frame and see if FCS is shown.