[c-nsp] drops on Vlan interface - sup720

[Andrew Fort]

On 22/06/2005, at 7:46 PM, Jerome Fleury wrote:

>
> SW1.GRE#sh int vlan11
> Vlan11 is up, line protocol is up
>   Hardware is EtherSVI, address is 0011.5d6a.dc00 (bia 0011.5d6a.dc00)
>   Description: F=B, E=BB1.GRE, P=ae0.11
>   MTU 4470 bytes, BW 1000000 Kbit, DLY 10 usec,
>      reliability 255/255, txload 176/255, rxload 37/255
>   Encapsulation ARPA, loopback not set
>   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 16:18:30
>   Input queue: 1/75/1040/744 (size/max/drops/flushes); Total output  
> drops: 0
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>   Queueing strategy: fifo
>   Output queue: 0/40 (size/max)
>   5 minute input rate 145433000 bits/sec, 86066 packets/sec
>   5 minute output rate 692230000 bits/sec, 95216 packets/sec

that's not insignificant traffic - obviously there's a reasonable  
amount also directed _at_ the interface ip address, hence the values  
you see in the input queue there, since the input queue on layer 3  
interfaces refers to stuff directed at the box itself (or process  
switched traffic - with any luck there should be very little of that  
on a sup720).  so, try:

int vlan 11
  hold-queue input 500

or some other value.  this'll give you some more room on the layer 3  
interface input queue, and you should see fewer drops.  flushes are  
another sign of full input queues (they are drops due to SPD,  
selective packet discard).

you can (should?) tweak the SPD settings also, since the thresholds  
for it are based on a 75-packet input queue.  see 'ip spd'.

-andrew