Can you help me explain how these are different?

Hi all,

First Set:
SW-3560-1(config-if)#srr-queue bandwidth limit ?
  <10-90>  enter bandwidth limit for interface  as percentage

SW-3560-1(config-if)#max-reserved-bandwidth ?
  <1-100>  Max. reservable bandwidth as % of interface bandwidth

Second Set:
SW-3560-1(config)#mls qos srr-queue input bandwidth 10 90

SW-3560-1(config)#mls qos srr-queue input priority-queue 1 bandwidth 10 --> Why set bandwidth for Q1 here again?

Thanks in advance




  • GabeGabe ✭✭

    Hi Martinl,

    I think there is a misunderstanding. I am trying to understand the difference between the two commands for each set (1 and 2) separately, I am not comparing the two commands in set 1 with the two commands in set 2.  Does that help understand my question?

  • JoeMJoeM ✭✭✭

    The default for max-reserved-bandwidth was 75%.  This command allowed us to change it from 0-100%

    But I think that this has changed in the newer IOS's.  


    Here is the IOS (not switch) command reference link for max-reserved-bandwidth.  It looks like it is being obsoleted (at least in the IOS).

    CiscoDoc:  max-reserved-bandwidth


    Effective with Cisco IOS XE Release 2.6, Cisco IOS Release 15.0(1)S, and Cisco IOS Release 15.1(3)T, the max-reservedbandwidthcommand is hidden. Although this command is still available in Cisco IOS software, the CLI interactive Help does not display it if you attempt to view it by entering a question mark at the command line. This command will be completely removed in a future release, which means that you will need to use the appropriate replacement command (or sequence of commands). For more information (including a list of replacement commands), see the "Legacy QoS Command Deprecation" feature document in the Cisco IOS XE Quality of Service Solutions Configuration Guide or the "Legacy QoS Command Deprecation" feature document in the Cisco IOS Quality of Service Solutions Configuration Guide.

    Usage Guidelines

    The max-reserved-bandwidth command is not supported in Cisco IOS Release 12.2SR or in 12.2SX. It is supported in 12.4T, but only up to the 12.4(20)T release in which HQF functionality was integrated.

    The sum of all bandwidth allocation on an interface should not exceed 75 percent of the available bandwidth on an interface. The remaining 25 percent of bandwidth is used for overhead, including Layer 2 overhead, control traffic, and best-effort traffic.

    If you need to allocate more than 75 percent for RSVP, CBWFQ, LLQ, IP RTP Priority, Frame Relay IP RTP Priority, Frame Relay PIPQ, or HQF, you can use the max-reserved-bandwidth command. The percent argument specifies the maximum percentage of the total interface bandwidth that can be used.

    If you do use the max-reserved-bandwidth command, make sure that not too much bandwidth is taken away from best-effort and control traffic.

  • GabeGabe ✭✭

    Hi JoeM

    Yes, the max-reserved-bandwidth command is gone in IOS 15.X but how is it different between doing it with that command (in codes that still have it) VS doing it through the srr queue. Are they mutually exclusive? Do they do the same thing?

    Any comments on the second set?


  • JoeMJoeM ✭✭✭

    Good question!  I really do not know Gabe.   In 12.4T(previous labs), I always focused on the other command (max-reserved), because the IOS would sometimes give warnings about it -- if more than 75% was needed to be reserved.  


    I think you are studying QoS from the previous workbook, right? I don't see anything in the new workbooks on this (v5 prep). 

    BTW, on the IOS side, I only see wrr-queue bandwidth

    Switch doc references has ssr-queue bandwidth limit


  • GabeGabe ✭✭

    I am just studying catalyst switch QoS, independently from WBs... I understand V5 does not have L2 QoS but I need to brush up QoS in this area for work purposes :)

    Thanks again.

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