Through this topology, I want to decrease the buffer size of R2 in order to generate an ICMP Source Quench Message, but I have no idea how to do it. I'm open to other suggestions to generate a Source Quench Message.

I'm using: Cisco Internetwork Operating System Software IOS (tm) 2600 Software (C2691-ENTSERVICESK9-M), Version 12.3(16)

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  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide your own answer and accept it.
    – Ron Maupin
    Aug 6, 2017 at 20:43

2 Answers 2


First, understand that you are doing something that you will likely never see in real life. I don't know if routers will even generate source quench responses.

Here is a document that discusses how to adjust buffers. I will quote only one sentence which summarizes the doument and my thoughts succinctly:

Note: Normally, interface buffers should not be tuned.


It is possible, but as Ron Trunk pointed out, it is not a good idea to do it by messing with the hardware. You can use QoS to do this also. Something like:

policy-map Test
 class class-default
  queue-limit <low> <high>

interface Serial0/0
 service-policy output Test

Cisco IOS Quality of Service Solutions Command Reference, Release 12.2

  • I think he needs to adjust input buffers, not output.
    – Ron Trunk
    May 11, 2016 at 23:29
  • That could be. Input on one side, or output on the other, or for a test, mess with the hardware. Between us, we gave him some options and stuff to learn :)
    – Ron Maupin
    May 11, 2016 at 23:31
  • I'm still performing the tests, I'm doing it for my article about ICMP, so I have to generate source quench message now May 11, 2016 at 23:54
  • you know, I was using hold-queue limiting to 1 packet, thus when input queue is full and CPU is not able to process the packet, the router'd drop these packets and I'd receive source quench message. May 12, 2016 at 0:26

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