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Recipe 11.18. Viewing Queue Parameters

Problem

You want to see how queuing is configured on an interface.

Solution

Cisco provides several useful commands for looking at an interface's queuing configuration and performance. The first of these is the show queue command:

Router#show queue FastEthernet0/0
  Input queue: 0/75/105/0 (size/max/drops/flushes); Total output drops: 0
  Queuing strategy: weighted fair
  Output queue: 0/1000/96/0 (size/max total/threshold/drops) 
     Conversations  0/1/128 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
     Available Bandwidth 75000 kilobits/sec


Router#

Use the show queuing command to look the router's queuing configuration in general:

Router#show queuing
Current fair queue configuration:

  Interface           Discard    Dynamic  Reserved  Link    Priority
                      threshold  queues   queues    queues  queues
  FastEthernet0/0     96         128      258       8       1    
  Serial0/0           64         256      37        8       1    
  Serial0/1           96         128      256       8       1    

Current DLCI priority queue configuration:
Current priority queue configuration:

List   Queue  Args
1      high   protocol ip          tcp port 198
1      high   protocol pppoe-sessi
2      high   protocol ip          udp port 199
3      low    default
3      high   protocol ip          list 101
Current custom queue configuration:
Current random-detect configuration:
Router#

Discussion

The show queue and show queuing commands augment the show interface output, which also shows important queuing information:

Router#show interface FastEthernet0/0
FastEthernet0/0 is up, line protocol is up 
  Hardware is AmdFE, address is 0001.9670.b780 (bia 0001.9670.b780)
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s, 100BaseTX/FX
  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 never
  Input queue: 0/75/105/0 (size/max/drops/flushes); Total output drops: 0
  Queuing strategy: weighted fair
  Output queue: 0/1000/96/0 (size/max total/threshold/drops) 
     Conversations  0/1/128 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
     Available Bandwidth 75000 kilobits/sec
  5 minute input rate 1000 bits/sec, 2 packets/sec
  5 minute output rate 2000 bits/sec, 2 packets/sec
     2495069 packets input, 181306312 bytes
     Received 2333309 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog
     0 input packets with dribble condition detected
     1927544 packets output, 197958017 bytes, 0 underruns
     0 output errors, 0 collisions, 21 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier
     0 output buffer failures, 0 output buffers swapped out
Router#

The show queue command is a good starting point when looking at queuing issues. It tells you what queuing algorithm is used, as well as information about any drops:

Router#show queue FastEthernet0/0
  Input queue: 0/75/105/0 (size/max/drops/flushes); Total output drops: 0
  Queuing strategy: weighted fair
  Output queue: 0/1000/96/0 (size/max total/threshold/drops) 
     Conversations  0/1/128 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
     Available Bandwidth 75000 kilobits/sec

In this case, you can see that the interface uses WFQ. This can be slightly deceptive because we actually configured this interface for CBWFQ. The Reserved Connections line indicates that no RSVP reservation queues have been allocated for this interface. So if you tried to use RSVP on this interface, it would not work right now.

The show queue command gives no output at all when you use Custom Queuing or Priority Queuing on an interface.

The first section of output from the show queuing command gives some useful summary information on fair queuing parameters:

Router#show queuing
Current fair queue configuration:

  Interface           Discard    Dynamic  Reserved  Link    Priority
                      threshold  queues   queues    queues  queues
  FastEthernet0/0     96         128      258       8       1    
  Serial0/0           64         256      37        8       1    
  Serial0/1           96         128      256       8       1

In this case, you can immediately see and compare the queue sizes between different interfaces.


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