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New Member

ASR9k CGNAT ISM scalability and performance design


I need some performance and scalability numbers and limitations of ASR9k ISM card for NAT44. Documentation says "at least 10 Gbps full-duplex bandwidth throughput". Some other presentation are mentioning 15 Gbps but I think this is probably pps limitation and not bandwidth.

So my question is:

  1. How many pps can one ISM card handle, I found somewhere around 1.5Mpps is this correct.
  2. Is this limitation separate for inbound and outbound connection or this is cumulative value.
  3. I read somewhere if we want to use full potential of ISM card that 2 pair of ServiceApp must be used. Is the limitation under section 1. referring to the one ServiceApp pair or two pairs. How many pps should each ServiceApp pair handle?
  4. How will we know when ISM can't handle any more traffic? Will "Inside to outside drops system limit reached" and "Inside to outside drops resource depletion" counters start to increase?


  • XR OS and Platforms
Cisco Employee

ASR9k CGNAT ISM scalability and performance design

Hi Omadon,

1) It would be about 5.5 - 6 Mpps per ISM. It may vary a little bit based on the packet length and other parameters like logging, etc.

2) It is cumulative value (for both I2O + O2I traffic)

3) Yes, you would need 2 ServiceApp pairs for maximum throughput. With 1 pair of ServiceApp, you would achieve 50% of throughput.

4) There will be drops at internal ports. It won't be reflected in any "show" XR CLI.



New Member

ASR9k CGNAT ISM scalability and performance design

Thanks Somnath