[c-nsp] Troubleshooting Lag between GigE interfaces

[Deepak Jain]

I would increase the size of the hold-queue "input" and see what happens 
after you clear the counters. You are definitely exhausting the input 
buffer on the 7513. The question is whether its just burstiness or 
something else -- you don't seem to be moving very much traffic on it to 
be a CPU issue. You do have output flow control on the 6509 on, but 
don't have the same setting on the 7513. That is the big problem I'd guess.

Paul Stewart wrote:

> We have a 7513 and a 6509 connected via GigE SX Fiber.  Frequently we
> see "lag" on the connection lasting 5-10 seconds causing 60-80ms delay.
> 
> When I look at the interfaces I see the following:
> 
> 7513
> 
> GigabitEthernet8/1/0 is up, line protocol is up
>   Hardware is cyBus GigabitEthernet Interface, address is 0001.64ef.a108
> (bia 0001.64ef.a108)
>   Description: Gig Fiber to 6509
>   Internet address is XXX.XXX.XXX.XXX/24
>   MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
>      reliability 255/255, txload 8/255, rxload 6/255
>   Encapsulation ARPA, loopback not set
>   Keepalive set (10 sec)
>   Full-duplex, 1000Mb/s, link type is autonegotiation, media type is SX
>   output flow-control is XOFF, input flow-control is unsupported
>   ARP type: ARPA, ARP Timeout 04:00:00
>   Last input 00:00:00, output 00:00:00, output hang never
>   Last clearing of "show interface" counters never
>   Input queue: 3/75/913188/2076260 (size/max/drops/flushes); Total
> output drops: 0
>   Queueing strategy: fifo
>   Output queue: 0/40 (size/max)
>   30 second input rate 26395000 bits/sec, 9394 packets/sec
>   30 second output rate 35145000 bits/sec, 9900 packets/sec
>      1790737826 packets input, 2276828279 bytes, 0 no buffer
>      Received 1895463 broadcasts, 0 runts, 0 giants, 34543 throttles
>      0 input errors, 0 CRC, 0 frame, 36 overrun, 0 ignored
>      0 watchdog, 520626 multicast, 0 pause input
>      0 input packets with dribble condition detected
>      1655202857 packets output, 359511296 bytes, 0 underruns
>      0 output errors, 0 collisions, 0 interface resets
>      0 babbles, 0 late collision, 0 deferred
>      2 lost carrier, 0 no carrier, 0 pause output
>      0 output buffer failures, 0 output buffers swapped out
> 
> 6509
> 
> GigabitEthernet1/2 is up, line protocol is up (connected)
>   Hardware is C6k 1000Mb 802.3, address is 0006.d65b.853d (bia
> 0006.d65b.853d)
>   Description: Connection to 7513
>   MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
>      reliability 255/255, txload 8/255, rxload 11/255
>   Encapsulation ARPA, loopback not set
>   Full-duplex, 1000Mb/s, media type is SX
>   input flow-control is off, output flow-control is on
>   Clock mode is auto
>   ARP type: ARPA, ARP Timeout 04:00:00
>   Last input never, output never, output hang never
>   Last clearing of "show interface" counters never
>   Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops:
> 0
>   Queueing strategy: fifo
>   Output queue: 0/40 (size/max)
>   5 minute input rate 43500000 bits/sec, 12035 packets/sec
>   5 minute output rate 33545000 bits/sec, 11573 packets/sec
>      5952975396 packets input, 2640933868846 bytes, 0 no buffer
>      Received 1696859 broadcasts (68504 multicast)
>      0 runts, 0 giants, 0 throttles
>      0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
>      0 watchdog, 0 multicast, 0 pause input
>      0 input packets with dribble condition detected
>      6088478711 packets output, 2200836239462 bytes, 0 underruns
>      0 output errors, 0 collisions, 1 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
> 
> The 6509 looks nice and clean but the 7513 shows a tonne of buffer
> issues it seems.  Is this a buffer issue that I should start trying to
> tune or would something else be the actual cause do you think?
> 
> Thanks in advance,
> 
> Paul
> 
> 
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