Default class drops

[therockyankur001]

Hi Everyone,

I'm seeing total drops in default class which (Summation) is not matching with total drops in different dscp values.

Output :-

Class-map: class-default (match-any)
155834394 packets, 125586331940 bytes
5 minute offered rate 12559000 bps, drop rate 2000 bps
Match: any
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/184494/0 >>>>>>>>>>>>>>>
(pkts output/bytes output) 155649900/125362734518
bandwidth 7236 kbps
Exp-weight-constant: 8 (1/256)
Mean queue depth: 0 packets
dscp Transmitted Random drop Tail drop Minimum Maximum Mark
pkts/bytes pkts/bytes pkts/bytes thresh thresh prob

default154672390/124851578978 0/0 0/0 51 136 1/5
1 0/0 0/0 0/0 51 136 1/5
2 0/0 0/0 0/0 51 136 1/5
3 0/0 0/0 0/0 51 136 1/5
4 17329/4118330 0/0 0/0 51 136 1/5
5 0/0 0/0 0/0 51 136 1/5
6 0/0 0/0 0/0 170 272 1/10
7 0/0 0/0 0/0 51 136 1/5
cs2 6553/836144 0/0 0/0 20 32 1/10
cs4 43451/22518406 0/0 16/12069 24 32 1/10
af41 442529/408177474 0/0 88/84544 28 32 1/10
ef 1024/113576 0/0 1/94 30 32 1/10
cs6 466009/75329192 5/502 102/11415 28 32 1/10
cs7 615/62418 0/0 0/0 30 32 1/10

Config :-

class class-default
bandwidth 7236
random-detect dscp-based
random-detect exponential-weighting-constant 8
random-detect dscp 0 51 136 5
random-detect dscp 1 51 136 5
random-detect dscp 2 51 136 5
random-detect dscp 3 51 136 5
random-detect dscp 4 51 136 5
random-detect dscp 5 51 136 5
random-detect dscp 6 170 272 10
random-detect dscp 7 51 136 5

12069+84544+94+11415+502 = 108624 = Sum of tail and random drops in default.

But there is a huge difference (75870) in total drops and sum of tail & random drops.
Need help to know how can i find reason of remaining drops in default.
Or I'm missing something in calculation.

Thanks in adavnce for your response.

Ankit

[Georg Pauwen]

Hello,

post the output of:

show interfaces interface
show queue interface
show queueing
show queueing random-detect

[therockyankur001]

Hello Georg,

Please find below O/P.

#sh int gig0/0/0
GigabitEthernet0/0/0 is up, line protocol is up
Hardware is ISR4331-3x1GE, address is 247e.1253.84b0 (bia 247e.1253.84b0)
MTU 1500 bytes, BW 40960 Kbit/sec, DLY 100 usec,
reliability 255/255, txload 81/255, rxload 36/255
Encapsulation 802.1Q Virtual LAN, Vlan ID 1., loopback not set
Keepalive not supported
Full Duplex, 100Mbps, link type is force-up, media type is RJ45
output flow-control is on, input flow-control is on
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:01, output 00:07:43, output hang never
Last clearing of "show interface" counters 1d01h
Input queue: 0/375/0/0 (size/max/drops/flushes); Total output drops: 199360
Queueing strategy: Class-based queueing
Output queue: 0/40 (size/max)
5 minute input rate 5837000 bits/sec, 1640 packets/sec
5 minute output rate 13068000 bits/sec, 2559 packets/sec
118627558 packets input, 42862792335 bytes, 0 no buffer
Received 0 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 45796 multicast, 0 pause input
171303405 packets output, 134330297312 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
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

Rest commands are not recognised -

#show queue?
% Unrecognized command

#show queue
^
% Invalid input detected at '^' marker

#show queueing?
% Unrecognized command

Thanks 

Ankit

[Joseph W. Doherty]

It might be due to the global queue limit only being 64.

btw, were do these numbers, "12069+84544+94+11415+502", come from?

[therockyankur001]

Hello Joseph,

it was calculated from attached O/P.

Thanks 

Ankit

[Joseph W. Doherty]

Ok, but I still don't see the numbers you're using. On your attachment, I see 5 random drops and about 200 WRED tail drops.

[ashok_boin]

Hi,

I think it's very difficult to match with this single output.

The Total drops accounts for several other reasons as well apart from WRED/Tail drops in the output. It also depends upon the platform.

Eg: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_mqc/configuration/xe-16-8/qos-mqc-xe-16-8-book/qos-limits-wred.html#GUID-88B6CDEC-E039-484B-9C1B-BEB238EE5C7A

In fact, it's only 212 packets dropped w.r.t WRED/Tail drops vs what's shown in 184494 total drops (Queue depth/ total drops talks about packets, not bytes).

Regards...

Ashok.