I got the job to limit the speed on a cisco 1GBit interface so that the link will have 100MBit symmetric and a burst limit of 1GBit. Its the internet uplink for a customer vlan. I am a bit confused because i read of traffic shaping vs policy map. I think i can issue

SW# configure terminal
SW (config)# interface GigabitEthernet 0/2
SW (config-if)# srr-queue bandwidth limit 20

because 100MBit symmetric means in both directions thats why i choose 20 percent of 1GBit. But how do i set the burst limit in this case?

Edit I found a video where someone used

rate-limit output <speed> <normal-burst> <max-burst> conform-action transmit exceed-action drop

so i think there are different ways. Can you help me which approach should i use?

Thank you very much

  • 1
    Shaping and/or policing on a switch is never very precise. Until you get into carrier class hardware (metro-e), it's mostly half-baked. In the cisco case, there are multiple commands necessary to really get anywhere. [ gregsowell.com/?p=3690 ] And your configs only act on egress.
    – Ricky
    Dec 15, 2022 at 23:52
  • 1
    It also depends GREATLY on the precise model of switch and IOS version installed on it. Each combination is a bit different. Also you will have to tinker as telling it to limit to a certain speed/bandwidth limit will usually mean it performs much lower most of the time so you have to work at it until you get the results you want in testing. Dec 16, 2022 at 1:57
  • 2
    @FrameHowitzer, the SG series does not run IOS.
    – Ron Maupin
    Dec 16, 2022 at 2:03
  • Yes, of course you are right. I assumed from the formatting of the configuration example. I guess I didn't see that the model was mentioned in the subject/question. Assuming the command line is that similar, I would guess the experience of needing to do tweaking in policing config will remain the same unless the implementation is totally different. Dec 26, 2022 at 5:51


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