Does the input/output rate of the interface take into account the Interframe Gap and preamble?

[mrisler.ig]

Hi Team,

So that is my question. When i run a "show interface Gi x/x", does the below ouput consider the Interframe gap and preamble, or just start counting the bits from the layer 2? 

5 minute input rate 47000 bits/sec, 90 packets/sec
  5 minute output rate 44000 bits/sec, 91 packets/sec

Thanks for your help! 

[Peter Paluch]

Hi,

In my best belief, these counters do not count Inter Frame Gap and preambles. If I may ask, what would be the purpose of taking these values into account?

Best regards,
Peter

[mrisler.ig]

eter,

Thanks very much for your reply! You are correct, it does not count inter frame gap and preamble. I just did a quick test with a JDSU Tester, a cisco switch ( WS-C3560G ) and a hard loop. When i configured CIR of 9.87 Mbps, on my loop i was receiving 10 Mbps of bandwidth ( Line speed Layer 1 ) and 9.87 Mbps of IR ( Layer 2). Then, i checked my interface`s input/output rate and saw the same result:

MIA-SW5#sh int gigabitEthernet 0/14 | i 30
  30 second input rate 9870000 bits/sec, 813 packets/sec
  30 second output rate 9870000 bits/sec, 813 packets/sec  

I was trying to understand the tool iPerf and the bandwidth command on it. I actually think they may refer bandwidth to throughput ( Layer 3), because when i configured 2Mbps with MTU of 1500, i was expecting to see 2 Mbps on my switch`s interface, but i saw 2.15 Mbps aprox. 

I will keep learning on how to use this tool.  

Thanks for your reply! 

[Joseph W. Doherty]

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You might also find, L2 framing overhead isn't counted either.