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QoS Referrence BW



I have the below QoS policy applied on the interface (This interface is connected to ISP). And the interface BW on the switch is 1Gbps while the actual ISP link BW is 100Mbps.

1- Now, these bandwidth percentage rules will inherit the reference BW from interface speed value 1Gbps, right? And in order to set proper reference BW value of 100Mbps, i must add the command "bandwidth" under the interface, correct?


interface GigabitEthernet1/0/12
description MPLS-ISP-1
switchport access vlan 55
history BPS
service-policy input NBAR-MARKING
service-policy output 2P6Q3T-WRED
ip nbar protocol-discovery

Core-SW#show policy-map 2P6Q3T-WRED
  Policy Map 2P6Q3T-WRED
    Class VOICE-PQ1
      priority level 1
     police rate percent 10
       conform-action transmit
       exceed-action drop
      queue-buffers ratio 5
    Class VIDEO-PQ2
      priority level 2
     police rate percent 23
       conform-action transmit
       exceed-action drop
      queue-buffers ratio 5
      bandwidth remaining 10 (%)
      queue-buffers ratio 5
      bandwidth remaining 15 (%)
      queue-buffers ratio 15
      queue-limit dscp af43 percent 80
      queue-limit dscp af42 percent 90
      bandwidth remaining 15 (%)
      queue-buffers ratio 10
      queue-limit dscp af33 percent 80
      queue-limit dscp af32 percent 90
      bandwidth remaining 15 (%)
      queue-buffers ratio 10
       percent-based wred

      dscp    min-threshold    max-threshold
      af21 (18)     80               100
      af22 (20)     70               100
      af23 (22)     60               100
      default (0)   -                -
      bandwidth remaining 7 (%)
      queue-buffers ratio 10
       percent-based wred

      dscp    min-threshold    max-threshold
      cs1  (8)      60               100
      af11 (10)     80               100
      af12 (12)     70               100
      af13 (14)     60               100
      default (0)   -                -
    Class class-default
      bandwidth remaining 38 (%)
      queue-buffers ratio 25
       percent-based wred

      dscp    min-threshold    max-threshold
      default (0)   80               100
Core-SW#show interfaces GigabitEthernet 1/0/12
TenGigabitEthernet1/0/12 is up, line protocol is up (connected)
Hardware is Ten Gigabit Ethernet, address is 7035.0906.450c (bia 7035.0906.450c)
Description: MPLS-ISP-1
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 15/255, rxload 6/255
Encapsulation ARPA, loopback not set
Keepalive not set
Full-duplex, 1000Mb/s, link type is auto, media type is 10/100/1000BaseTX SFP
input flow-control is on, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output 00:00:01, output hang never
Last clearing of "show interface" counters never
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 12994
Queueing strategy: Class-based queueing
Output queue: 0/40 (size/max)
5 minute input rate 25545000 bits/sec, 4735 packets/sec
5 minute output rate 59167000 bits/sec, 6163 packets/sec
16203203046 packets input, 12945308740063 bytes, 0 no buffer
Received 1264967 broadcasts (1264941 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 1264941 multicast, 0 pause input
0 input packets with dribble condition detected
12367851628 packets output, 10243344964139 bytes, 0 underruns
Output 3108 broadcasts (0 multicasts)
0 output errors, 0 collisions, 2 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


Joseph W. Doherty
Hall of Fame Expert

#1 Yes and yes (assuming available bandwidth is less then what interface is physically running at).

Thank you for your answer. Is there a reference for this? As i've been trying to find but couldn't. What i noticed from that shows that it indeed inherit the interface speed.... but couldn't find a reference that says it will inherit from (bandwidth) command. It is logical though, but i need a reference.

"Is there a reference for this?"

I believe there is/are, but cannot point you at one off-the-top-of-my-head.

Most likely reference will be made either in a manual discussing using percentage options, on QoS features like police and/or shape, possible the bandwidth command itself (explaining what it can impact), and/or a white paper or technote further explaining usage of QoS.