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3550 Interface Stats

Two 3550s are connected via fiber. Please take a look at their g0/1 five minute input and output rates. Why are the bps numbers not almost exact inverses of one another? Why is the second switch's pps output rate only 2?

Switch1#show int g0/1 GigabitEthernet0/1 is up, line protocol is up (connected) Hardware is Gigabit Ethernet, address is 0011.933b.a999 (bia

0011.933b.a999) MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 1000Mb/s, media type is LX input flow-control is off, output flow-control is off ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:01, output 00:00:01, output hang never Last clearing of "show interface" counters 00:11:20 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue: 0/40 (size/max) 5 minute input rate 340000 bits/sec, 83 packets/sec 5 minute output rate 896000 bits/sec, 93 packets/sec 51441 packets input, 21742862 bytes, 0 no buffer Received 373 broadcasts (0 multicast) 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog, 373 multicast, 0 pause input 0 input packets with dribble condition detected 72123 packets output, 82788904 bytes, 0 underruns 0 output errors, 0 collisions, 0 interface resets 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier, 0 PAUSE output 0 output buffer failures, 0 output buffers swapped out

Switch2#show int g0/1 GigabitEthernet0/1 is up, line protocol is up Hardware is Gigabit Ethernet, address is 000c.85ca.a719 (bia

000c.85ca.a719) MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 1000Mb/s, link type is autonegotiation, media type is LX output flow-control is off, input flow-control is off ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:03, output 00:00:01, output hang never Last clearing of "show interface" counters 00:11:38 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue :0/40 (size/max) 5 minute input rate 851000 bits/sec, 58 packets/sec 5 minute output rate 261000 bits/sec, 2 packets/sec 75635 packets input, 87679638 bytes, 0 no buffer Received 1138 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog, 742 multicast, 0 pause input 0 input packets with dribble condition detected 53517 packets output, 21837450 bytes, 0 underruns 0 output errors, 0 collisions, 0 interface resets 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier, 0 PAUSE output 0 output buffer failures, 0 output buffers swapped out
Reply to
bobneworleans
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Full-duplex, 1000Mb/s, link type is autonegotiation, media type is LX

" 5 minute output rate 261000 bits/sec, 2 packets/sec" This discrepecy is surely a bug?

It might be something to do with the very low traffic rate, The rates here are not exactly 'interesting' with respect to a gigabit interface. I notice that the packets/bytes in/out correspond well.

My experience of the rate counters is that they are generally OK.

You chuold check the version in the two boxes and consider a change if you need to fix it.

Note that the 5 min counter takes account of data over a period of about 20 minuts.

Look up exponential weighted average on CCO.

Reply to
anybody43

also be aware that you can change the time period using the interface "load-interval" command

int

Reply to
Merv

Well, you're right. The two IOS versons are not the same. Switch1: Version 12.1(20)EA1a Switch2: Version 12.1(12c)EA1

Thanks.

Reply to
bobneworleans

CCO only has 12.1(22)EA* available for donwload, so if you have access that might be worth a try

Reply to
Merv

Merv wrote:

Yes I do that a lot. Fine idea.

Be aware that EIGRP (IRGP too?) may use the "Load" value to compute its metrics.

I think that is is always a good idea to emphasise that it is not a "30 second period". 'cos its not:-))

It's an Exponential Weighted Average with a Time Constant of 30 seconds.

IIRC - (It's been a while) In the case where the Time Constant is set to 5 mins (the default) and when the rate counters are reporting zero load to begin with and when the interface is offered a step change in load from zero to 100%, the reported value takes about 20 minutes to reach 100%.

I don't fully understand the mathematics (math in the US?:) but I have done the experiments.

Reply to
anybody43

Greetings,

... chopped ...

It may also be worth noting that if the "5 minute input rate" can take up to 20 mins to produce stable readings, in teh case of teh output above the counters were only cleared 11 mins ago.

Cheers.............pk.

Reply to
Peter

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