[c-nsp] Giants and input errors but no MTU mismatch 7600-to-4948

[John Neiberger]

We're not doing any q-in-q or mpls. There is nothing unusual about
this config at all. I'm stumped! To make matters even more
entertaining, I just checked the other switch in this pair of
switches:

 0 runts, 1894463 giants, 0 throttles
     1894463 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

That switch has the exact same trunk connection to a different 7600
and it is also seeing input errors. I'm starting to think it's a bug
in the 4948 code and maybe it's just misreporting somehow. It's very
strange.


On Wed, Sep 19, 2012 at 12:30 PM, Aaron <aaron1 at gvtc.com> wrote:
> Would double tagging (qnq) sitting atop g3/3 (service instances or svi's)
> cause this?  Or mpls-enabled svi's sitting on top of g3/3 perhaps ?
> (brainstorming as I'm not sure what to make of it)
>
> Aaron
>
>
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of John Neiberger
> Sent: Wednesday, September 19, 2012 12:20 PM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] Giants and input errors but no MTU mismatch 7600-to-4948
>
> I have an interface on a 4948 that is reporting increasing giants and input
> errors. The MTU is the default 1500 and so is the interface on the other
> side of the link. This is a dot1q trunk, if that is relevant.
>
> 7600 Side:
>
> GigabitEthernet3/3 is up, line protocol is up (connected)
>   Hardware is C6k 1000Mb 802.3, address is 7081.058f.471e (bia
> 7081.058f.471e)
>   MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
>      reliability 255/255, txload 6/255, rxload 6/255
>   Input queue: 0/2000/15/0 (size/max/drops/flushes); Total output drops:
> 52636
>   Queueing strategy: fifo
>   Output queue: 0/40 (size/max)
>   30 second input rate 25560000 bits/sec, 3911 packets/sec
>   30 second output rate 25889000 bits/sec, 2481 packets/sec
>      103422624782 packets input, 96894603872012 bytes, 0 no buffer
>      Received 421340 broadcasts (390040 multicasts)
>      0 runts, 0 giants, 0 throttles
>      0 input errors, 0 CRC, 0 frame, 15 overrun, 0 ignored
>      0 watchdog, 0 multicast, 0 pause input
>      0 input packets with dribble condition detected
>
> 4948 Side:
>
> GigabitEthernet1/46 is up, line protocol is up (connected)
>   Hardware is Gigabit Ethernet Port, address is e05f.b919.522d (bia
> e05f.b919.522d)
>   MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
>      reliability 255/255, txload 6/255, rxload 7/255
>   Last input 00:00:00, 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 27555000 bits/sec, 2622 packets/sec
>   5 minute output rate 25030000 bits/sec, 3827 packets/sec
>      103432206170 packets input, 100545576069607 bytes, 0 no buffer
>      Received 401659764 broadcasts (377463573 multicasts)
>      0 runts, 1892602 giants, 0 throttles
>      1892602 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
>      0 input packets with dribble condition detected
>
> Any idea how I could be getting giants inbound to the 4948 when the
> interface on the 7600 is set to 1500? I could see it if both sides were not
> set to dot1q, but they are:
>
> Gi3/3               on           802.1q         trunking      1
>
> Gi1/46             on           802.1q         trunking      1
>
> What in the world is going on here?
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