Mastering QoS

JackaceJackace Member Posts: 335
I'm looking to tackle QoS in the coming months and really get proficient with it. My question to you all is how best to do this in a lab environment?


  • EMcCalebEMcCaleb Member Posts: 63 ■■■□□□□□□□
    There are so many sub-categories to QoS it's difficult to give a concise answer. Some things are hard to test without some rudimentary traffic generation, I recommend Ostinato but I realize there are many many others out there. Secondly, a lot can be accomplished just by "ping" and setting the TOS field (under the extended ping option). Believe it or not, you can get a LOT of truth data just from that. Also, it will help you quickly understand how the TOS field works. You can then write access-lists that log on TOS and/or the comparable DSCP as you begin to manipulate your environment.

    I would also recommend using IP SLA in conjunction with your QoS studies as a way of killing two birds with one stone.

    Finally, play with Wireshark -a lot- to observe the consequences

    These are some of the things I did to help me grasp QoS.

  • lrblrb Member Posts: 526
    Theory: Read QoS official cert guide. Now that L2 QoS is not in the lab, you can skip over chapter 9 and any of the switch QoS config guides on

    Lab: Either use a workbook such as those from INE, Narbik or make up your own scenarios. Both of these training vendors will utilize the copy and ping commands to show the affects of configuring shapers, policers, classifiers, etc. You can also throw in using a tool called iperf to generate random traffic at whatever rate you want.

    I'm guessing you're studying for the CCIEv5 R&S lab? Note that QoS is a much smaller part on this version than it was on the previous one. The Infra Services section is 15%, which means they would have not ask you anything about DHCPv4/v6, FHRPs, and NAT for that 15% to be completely filled up with QoS questions. I don't see this as likely so I would estimate QoS would account for maybe 5-8% of the lab. The point of saying this is that I wouldn't spend weeks and weeks doing nothing but QoS labs for hours every day. YMMV

    Good luck with the study :)
  • JackaceJackace Member Posts: 335
    Thank you for the advice so far. Yes I am preparing for the v5 version of the exam, but I would also like to really get a solid grasp on QoS. I will need a lot of the more advanced stuff once we implement some new things at work which should be done by the end of this year or first of next. Also I left a few things off my OP I should have included. My lab will most likely be GNS3 (with possibly a break out switch) so tools that I can use with that would be most helpful. I have read the Cert guide twice as well as QoS in IP/MPLS networks. I think I have a pretty good grasp on the theory now, but I just need to take the theory and get practice configuring it so I can really learn it. I don't get the opportunity to really play with QoS at work. Working for a SP we don't do a lot of new things with QoS and everything we do use now is just a copy paste from a known working config. Once in a great while I might have to play with QoS for a customer or something, but that might be once or twice a year at most.
  • Roy4USARoy4USA Member Posts: 22 ■□□□□□□□□□
    I would not have believed how much QoS Configurations vary from platform to platform and even on different blade types in the same platform, had I not configured them. QoS Configurations are very hardware specific. There is a new Cisco Press Book out on End to End QoS that goes over the differences on the various platforms. I hope to get time to read it soon.

    Today I watched the first INE Routing and Switching ATC v4.5 QoS Introduction Video and liked it. Everything Brian said in that video makes sense to me now.

    Labbing QoS for CCIE R&S v5, I'd probably start by trying to lab that with up virtual routers first and then some physical 3560 and 3570 switches. I have not tested QoS on Virtual Routers yet. I wonder if anybody has been able to use Virtual Routers to lab QoS?
  • gorebrushgorebrush Member Posts: 2,743 ■■■■■■■□□□
    I'd have thought now that the platform specific stuff is gone - it'll mainly be learning about the queuing mechanisms - and how the class maps work etc.

    A lot of the complexity has been removed for v5.
  • lrblrb Member Posts: 526
    Roy4USA wrote: »
    Labbing QoS for CCIE R&S v5, I'd probably start by trying to lab that with up virtual routers first and then some physical 3560 and 3570 switches. I have not tested QoS on Virtual Routers yet. I wonder if anybody has been able to use Virtual Routers to lab QoS?

    The v5 lab is done completely in IOU/IOL now and L2 QoS has been removed too. I've done some QoS labbing on IOU and it seemed to work okay for the most part.
  • rareairrareair Member Posts: 6 ■■□□□□□□□□
    I had an esxi-server avaliable when I was practising for the v4-lab, and I combined gns3 with virtual windows machines. That makes it simple to practice policing and shaping with for example ftp, where you setup one ftp server and one client, and then put a gns-router between them with qos-config. For marking and queueing, I relied on the show-commands to see that traffic was tagged and queued correctly. QOS L3 is a lot easier to practice and verify than L2, so you're lucky there.

    The MQC is actually easy once you get the hang of it, and quite fun. Good luck to you!
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