11-16-2017 10:27 AM - edited 03-08-2019 12:46 PM
We have wireless access points connect to c3750 switches version 12.2(53)SE2. The wireless performance is slow. I noticed packet drops on the switch interfaces connected to APs:
show mls qos interface f3/0/26 statistics
output queues enqueued:
queue: threshold1 threshold2 threshold3
-----------------------------------------------
queue 0: 2 0 1064
queue 1: 322452 682655 4984891
queue 2: 0 0 2273818
queue 3: 0 139438 2757101931
output queues dropped:
queue: threshold1 threshold2 threshold3
-----------------------------------------------
queue 0: 0 0 0
queue 1: 0 0 0
queue 2: 0 0 0
queue 3: 0 20103 171024282
Currently the switch port is configured as:
interface FastEthernet3/0/26
description AP
switchport access vlan XXXX
switchport mode access
switchport port-security aging time 1
switchport port-security aging type inactivity
srr-queue bandwidth share 10 10 60 20
mls qos trust dscp
snmp trap mac-notification change added
snmp trap mac-notification change removed
no mdix auto
storm-control broadcast level pps 25 10
storm-control multicast level pps 25 10
storm-control action trap
spanning-tree portfast
end
Question: I know the "srr-queue bandwidth share 10 10 60 20" command sets bandwidth share for the four queues. On the "show mls qos interface f3/0/26 statistics" command, I see lots of packet drops on queue 3 and the queue numbers from that command starts from queue 0. So is the queue 0 actually the first queue in the "srr-queue bandwidth share 10 10 60 20" command? In another words, does queue 0 gets 10% and queue 3 gets 20% bandwidth from the above srr-queue command? If that is the case, I think I should increase the bandwidth share for queue 3?
Thanks.
Solved! Go to Solution.
11-17-2017 09:53 AM - edited 11-20-2017 09:53 AM
You can try pushing your drop thresholds up, even to max for all. (Later IOS versions support 1600 3200 max, earlier versions 400 max.)
You can also try cutting way back (try 25, or less, for all queues) on your "reserved" settings. Your settings leave no pool buffers in queue set 2, and few in queue set 1, to "borrow" when needed.
11-17-2017 12:18 PM
11-16-2017 11:54 AM
11-16-2017 12:06 PM
s1409_LIB(71)2-2#sh interface Fa 3/0/26 controll
FastEthernet3/0/26 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 001a.a180.cc9e (bia 001a.a180.cc9e)
Description: AP
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 102/255, rxload 9/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:09, output 00:00:52, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 171907274
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 3783000 bits/sec, 2479 packets/sec
5 minute output rate 40090000 bits/sec, 5889 packets/sec
2897705676 packets input, 719234427386 bytes, 0 no buffer
Received 377384 broadcasts (294833 multicasts)
0 runts, 0 giants, 0 throttles
5 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 294833 multicast, 0 pause input
0 input packets with dribble condition detected
7091168674 packets output, 5676998644242 bytes, 0 underruns
0 output errors, 0 collisions, 0 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
Transmit FastEthernet3/0/26 Receive
3393529393 Bytes 1978486710 Bytes
2792820142 Unicast frames 2897347672 Unicast frames
2959679 Multicast frames 294833 Multicast frames
476804 Broadcast frames 82551 Broadcast frames
0 Too old frames 1867067097 Unicast bytes
0 Deferred frames 105974603 Multicast bytes
0 MTU exceeded frames 5441768 Broadcast bytes
0 1 collision frames 0 Alignment errors
0 2 collision frames 0 FCS errors
0 3 collision frames 0 Oversize frames
0 4 collision frames 0 Undersize frames
0 5 collision frames 0 Collision fragments
0 6 collision frames
0 7 collision frames 569398 Minimum size frames
0 8 collision frames 145100068 65 to 127 byte frames
0 9 collision frames 2428678185 128 to 255 byte frames
0 10 collision frames 67058487 256 to 511 byte frames
0 11 collision frames 71811749 512 to 1023 byte frames
0 12 collision frames 184507174 1024 to 1518 byte frames
0 13 collision frames 0 Overrun frames
0 14 collision frames 0 Pause frames
0 15 collision frames
0 Excessive collisions 5 Symbol error frames
0 Late collisions 0 Invalid frames, too large
0 VLAN discard frames 0 Valid frames, too large
0 Excess defer frames 0 Invalid frames, too small
2875289289 64 byte frames 0 Valid frames, too small
94968290 127 byte frames
372819643 255 byte frames 0 Too old frames
82877497 511 byte frames 0 Valid oversize frames
93257585 1023 byte frames 0 System FCS error frames
3572011617 1518 byte frames 0 RxPortFifoFull drop frame
0 Too large frames
0 Good (1 coll) frames
0 Good (>1 coll) frames
So does the "queue 0" in "sh mls qos interface statistics" command actually means "queue 1"from the queue-set command? And "queue 3" means "queue 4"? This part is confusing to me.
Thanks.
11-16-2017 11:20 PM
11-17-2017 06:41 AM
So does the "queue 0" in "sh mls qos interface statistics" command actually means "queue 1"from the queue-set command? And "queue 3" means "queue 4"?
Yes, sometimes the 3750 refers to its egress queues as 0..3 and sometimes 1..4.
11-17-2017 06:52 AM
11-17-2017 07:26 AM
Thank you for the replies.
I changed the "srr-queue bandwidth share 10 10 60 20"to "srr-queue bandwidth share 10 10 20 60" to give queue 3 more bandwidth because queue 3 has lots of drops and no drops for other queues:
output queues dropped:
queue: threshold1 threshold2 threshold3
-----------------------------------------------
queue 0: 0 0 0
queue 1: 0 0 0
queue 2: 0 0 0
queue 3: 0 20103 173799603
But still see packet drops at queue3 after this change.
I also changed the interface to use queue-set2 instead of queue-set1 as queue-set2 has more buffers for queue3:
#sh mls qos queue-set 2
Queueset: 2
Queue : 1 2 3 4
----------------------------------------------
buffers : 16 6 17 61
threshold1: 149 118 41 42
threshold2: 149 118 68 72
reserved : 100 100 100 100
maximum : 149 235 272 242
#sh mls qos queue-set 1
Queueset: 1
Queue : 1 2 3 4
----------------------------------------------
buffers : 10 10 26 54
threshold1: 138 138 36 20
threshold2: 138 138 77 50
reserved : 92 92 100 67
maximum : 138 400 318 400
Still has packet drops on queue3. Any other suggestions I should try?
The interface is used to connect a Cisco c3702 AP and that AP has lots of clients. Maybe there isn't much we can do with an old C3750 switch and we need to upgrade to c3850. Just trying to see if there are any parameters we can adjust to make it work.
11-17-2017 09:53 AM - edited 11-20-2017 09:53 AM
You can try pushing your drop thresholds up, even to max for all. (Later IOS versions support 1600 3200 max, earlier versions 400 max.)
You can also try cutting way back (try 25, or less, for all queues) on your "reserved" settings. Your settings leave no pool buffers in queue set 2, and few in queue set 1, to "borrow" when needed.
11-17-2017 11:12 AM
I understand your points. Now I use queue-set 1 for the interface and it already sets to maximum 400 for queue 4. I am only concerning queue 4 now as it is the only queue dropping packets.
I changed the "reserved" setting to 25 for all queues:
#show mls qos queue-set 1
Queueset: 1
Queue : 1 2 3 4
----------------------------------------------
buffers : 10 10 26 54
threshold1: 138 138 36 20
threshold2: 138 138 77 50
reserved : 25 25 25 25
maximum : 138 400 318 400
The issue is still not resolved.
output queues enqueued:
queue: threshold1 threshold2 threshold3
-----------------------------------------------
queue 0: 2 0 1105
queue 1: 323933 685761 5078521
queue 2: 0 0 2316935
queue 3: 0 139593 2939270834
output queues dropped:
queue: threshold1 threshold2 threshold3
-----------------------------------------------
queue 0: 0 0 0
queue 1: 0 0 0
queue 2: 0 0 0
queue 3: 0 20103 176129847
Thanks.
11-17-2017 12:18 PM
11-17-2017 02:09 PM
The drop frequency did not change much after the previous change.
The configurable threshold for max is 1-3200. I increased to 2000 and it made significant improvement. I still see packet drops but much less than before. My wireless speed test result from the AP is also greatly improved from 2Mbps to 10Mbps. Thanks a lot!
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