Hi All,
I have noticed that a number of the interfaces on a Cisco 6509 switch are reporting output drops. The links in question are all using BT "LES" circuits (BT ethernet extension circuits) to connect to Cisco 3560's at the remote sites. There are no drops (Input or output) recorded on the remote ends.
Each interface in question is on a CEF720 48 port 10/100/1000mb Ethernet WS-X6748-GE-TX card in the chassis. The interface config is:
interface GigabitEthernet3/39
description Connected to
switchport
switchport trunk encapsulation dot1q
switchport trunk native vlan 36
switchport trunk allowed vlan 36,999
switchport mode trunk
no ip address
speed 100
duplex full
wrr-queue bandwidth 5 25 70
wrr-queue queue-limit 5 25 40
wrr-queue random-detect min-threshold 1 80 100 100 100 100 100 100 100
wrr-queue random-detect min-threshold 2 80 100 100 100 100 100 100 100
wrr-queue random-detect min-threshold 3 50 60 70 80 90 100 100 100
wrr-queue random-detect max-threshold 1 100 100 100 100 100 100 100 100
wrr-queue random-detect max-threshold 2 100 100 100 100 100 100 100 100
wrr-queue random-detect max-threshold 3 60 70 80 90 100 100 100 100
mls qos trust dscp
end
Speed is hardcoded to 100Mbps Full Duplex on both ends. In this example VLAN 36 is used as the Layer 3 routed interface for the connection.
A "Show interface x/x" shows:
NPLYG28-C-1#sho int gi 3/39
GigabitEthernet3/39 is up, line protocol is up (connected)
Hardware is C6k 1000Mb 802.3, address is 001b.2ab4.71a6 (bia 001b.2ab4.71a6)
Description: Connected to Corsham Court LES100
MTU 1500 bytes, BW 100000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s
input flow-control is off, output flow-control is on
Clock mode is auto
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:46, output 00:00:45, output hang never
Last clearing of "show interface" counters 01:22:39
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 253
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 59000 bits/sec, 39 packets/sec
5 minute output rate 271000 bits/sec, 92 packets/sec
410316 packets input, 72828784 bytes, 0 no buffer
Received 2203 broadcasts (1651 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
0 input packets with dribble condition detected
793089 packets output, 548616558 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
So, its had about 253 drops in the last hour or so. The "Show queueing" output shows:
NPLYG28-C-1#show queueing int gi 3/39
Interface GigabitEthernet3/39 queueing strategy: Weighted Round-Robin
Port QoS is enabled
Trust state: trust DSCP
Extend trust state: not trusted [COS = 0]
Default COS is 0
Queueing Mode In Tx direction: mode-cos
Transmit queues [type = 1p3q8t]:
Queue Id Scheduling Num of thresholds
-----------------------------------------
01 WRR 08
02 WRR 08
03 WRR 08
04 Priority 01
WRR bandwidth ratios: 5[queue 1] 25[queue 2] 70[queue 3]
queue-limit ratios: 5[queue 1] 25[queue 2] 40[queue 3] 15[Pri Queue]
queue tail-drop-thresholds
--------------------------
1 70[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
2 70[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
3 100[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
queue random-detect-min-thresholds
----------------------------------
1 80[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
2 80[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
3 50[1] 60[2] 70[3] 80[4] 90[5] 100[6] 100[7] 100[8]
queue random-detect-max-thresholds
----------------------------------
1 100[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
2 100[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
3 60[1] 70[2] 80[3] 90[4] 100[5] 100[6] 100[7] 100[8]
WRED disabled queues:
queue thresh cos-map
---------------------------------------
1 1 0
1 2 1
1 3
1 4
1 5
1 6
1 7
1 8
2 1 2
2 2 3 4
2 3
2 4
2 5
2 6
2 7
2 8
3 1 6 7
3 2
3 3
3 4
3 5
3 6
3 7
3 8
4 1 5
Queueing Mode In Rx direction: mode-cos
Receive queues [type = 1q8t]:
Queue Id Scheduling Num of thresholds
-----------------------------------------
01 WRR 08
WRR bandwidth ratios: 100[queue 1]
queue-limit ratios: 100[queue 1]
queue tail-drop-thresholds
--------------------------
1 100[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
queue thresh cos-map
---------------------------------------
1 1 0 1 2 3 4 5 6 7
1 2
1 3
1 4
1 5
1 6
1 7
1 8
Packets dropped on Transmit:
queue dropped [cos-map]
---------------------------------------------
1 253 [0 1 ]
2 0 [2 3 4 ]
3 0 [6 7 ]
4 0 [5 ]
Packets dropped on Receive:
BPDU packets: 0
queue dropped [cos-map]
---------------------------------------------
1 0 [0 1 2 3 4 5 6 7 ]
So, all of this info tells me that 250 packets have been dropped in queue 1. Can anyone point in in the direction of any possible cause for this? The interfaces themselves have extremely low utilisation - our day to day SNMP monitoring of them indicates a peak of about 20% absolulte max, general use sits at about 2%.
One thing I have noticed is that outbound flow control is set to "on" - could this be a cause of a confluct with the QoS settings on the interface?
Any help much appreciated,
Many thanks
Jonathan
