I'm certainly not an expert and just learning how to read through all of these numbers. I've been doing a QOS test on a production switch (2960-S) and when I use auto qos trust dscp (while this is for VOIP, I want to trust dscp not cos) the number of drops go through the roof on certain interfaces. I've been monitoring one user interface in particular that doesn't even use VOIP so honestly, there would never be any packets for the priority queue, they work on large graphics files for print. OK, I can just disable QOS on that interface, but that's not exactly the answer because I'd like to know how to possibly better fine tune it. I ran the various mls qos show commands and I see QOS is dropping packets from queues 3 and 4 (most other traffic on our network is just marked 0.) My concern is that I thought with srr (shared) the additional bandwidth allocated to other queues is shared when not in use -- so why are so many packets dropping on these interfaces? The pertinent config is below:
mls qos map cos-dscp 0 8 16 24 32 46 48 56
mls qos srr-queue output cos-map queue 1 threshold 3 4 5
mls qos srr-queue output cos-map queue 2 threshold 1 2
mls qos srr-queue output cos-map queue 2 threshold 2 3
mls qos srr-queue output cos-map queue 2 threshold 3 6 7
mls qos srr-queue output cos-map queue 3 threshold 3 0
mls qos srr-queue output cos-map queue 4 threshold 3 1
mls qos srr-queue output dscp-map queue 1 threshold 3 32 33 40 41 42 43 44 45
mls qos srr-queue output dscp-map queue 1 threshold 3 46 47
mls qos srr-queue output dscp-map queue 2 threshold 1 16 17 18 19 20 21 22 23
mls qos srr-queue output dscp-map queue 2 threshold 1 26 27 28 29 30 31 34 35
mls qos srr-queue output dscp-map queue 2 threshold 1 36 37 38 39
mls qos srr-queue output dscp-map queue 2 threshold 2 24
mls qos srr-queue output dscp-map queue 2 threshold 3 48 49 50 51 52 53 54 55
mls qos srr-queue output dscp-map queue 2 threshold 3 56 57 58 59 60 61 62 63
mls qos srr-queue output dscp-map queue 3 threshold 3 0 1 2 3 4 5 6 7
mls qos srr-queue output dscp-map queue 4 threshold 1 8 9 11 13 15
mls qos srr-queue output dscp-map queue 4 threshold 2 10 12 14
mls qos queue-set output 1 threshold 1 100 100 50 200
mls qos queue-set output 1 threshold 2 125 125 100 400
mls qos queue-set output 1 threshold 3 100 100 100 400
mls qos queue-set output 1 threshold 4 60 150 50 200
mls qos queue-set output 1 buffers 15 25 40 20
mls qos
interface GigabitEthernet1/0/14
switchport access vlan 95
switchport mode access
srr-queue bandwidth share 1 30 35 5
priority-queue out
mls qos trust dscp
no cdp enable
spanning-tree portfast
spanning-tree bpduguard enable
#show int g1/0/14 (by the way, don't know why it says fifo -- presumably a cosmetic issue)
GigabitEthernet1/0/14 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is 1caa.0773.638e (bia 1caa.0773.638e)
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
reliability 255/255, txload 5/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output 00:00:00, output hang never
Last clearing of "show interface" counters 00:34:43
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 1316
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 253000 bits/sec, 129 packets/sec
5 minute output rate 2053000 bits/sec, 243 packets/sec
118918 packets input, 28164709 bytes, 0 no buffer
Received 86 broadcasts (76 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 76 multicast, 0 pause input
0 input packets with dribble condition detected
214263 packets output, 211690502 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
*** the command below is run on a different interface because I temporarily disabled the interface I was monitoring ***
#show mls qos int g1/0/14 statistics
GigabitEthernet1/0/14 (All statistics are in packets)
dscp: incoming
-------------------------------
0 - 4 : 100285940 0 0 0 0
5 - 9 : 0 0 50 0 0
10 - 14 : 1209 0 0 0 0
15 - 19 : 0 0 0 18 0
20 - 24 : 1 0 0 0 0
25 - 29 : 0 0 0 0 0
30 - 34 : 0 0 0 0 0
35 - 39 : 0 0 0 0 0
40 - 44 : 0 0 0 0 0
45 - 49 : 0 2705 0 185 0
50 - 54 : 0 0 0 0 0
55 - 59 : 0 0 0 0 0
60 - 64 : 0 0 0 0
dscp: outgoing
-------------------------------
0 - 4 : 163549042 0 5 0 5
5 - 9 : 0 20 1994068 0 0
10 - 14 : 540049 0 0 0 0
15 - 19 : 0 0 0 10496 0
20 - 24 : 924 0 0 0 112
25 - 29 : 0 3 0 0 0
30 - 34 : 0 130 10486 0 84521
35 - 39 : 1 0 0 0 181
40 - 44 : 2 0 0 0 1
45 - 49 : 0 7030 0 837854 0
50 - 54 : 0 0 0 0 0
55 - 59 : 0 0 0 0 0
60 - 64 : 0 0 0 0
cos: incoming
-------------------------------
0 - 4 : 100304639 0 0 0 0
5 - 7 : 0 0 0
cos: outgoing
-------------------------------
0 - 4 : 166477516 16120 14876 15320 26437
5 - 7 : 18894 870353 488066
output queues enqueued:
queue: threshold1 threshold2 threshold3
-----------------------------------------------
queue 0: 0 0 1183
queue 1: 1119752 45666 772262
queue 2: 0 0 15067159
queue 3: 0 3104 150931868
output queues dropped:
queue: threshold1 threshold2 threshold3
-----------------------------------------------
queue 0: 0 0 0
queue 1: 0 0 0
queue 2: 0 0 2103
queue 3: 0 0 9003
Policer: Inprofile: 0 OutofProfile: 0
